A lot of the confusion stems from the fact that USB-C, or more accurately, USB Type-C, refers to a 24-pin connector. This connector is utilized by various interface protocols, including USB, Thunderbolt, PCIe, HDMI, DisplayPort, among others.

Before this there were USB Type-A connectors, where the "A" indicated the host connector, and USB Type-B connectors, where the "B" signified the device or peripheral connector.

USB Type-C connectors have been designed such that they have the flexibility to serve as either host or device connectors.

Thunderbolt is a protocol designed for connecting devices to computers, initially released in 2011. Nowadays, we're primarily focused on Thunderbolt 3 and Thunderbolt 4. Both of these advanced protocols utilize the USB-C connector.

The Thunderbolt 3 protocol, introduced by Intel, is a significant update to the Thunderbolt technology, offering advancements in speed, flexibility, and connectivity. 

• It's super-fast: Thunderbolt 3 can move your files and videos at a mind-blowing speed of up to 40 Gbps. That's double the speed of its predecessor and 8 times quicker than USB 3.0!
• USB-C connector: The cool, reversible USB-C connector means no more fumbling around trying to plug in your devices. Plus, it's the same port for charging, data, and video, so one port can do it all.
• Dual 4K displays: Imagine having two 4K monitors displaying crystal-clear visuals at 60 Hz, or even one mega 5K display.
• Link up devices: You can connect up to six devices together with just one Thunderbolt 3 port. It's like having a super-efficient train of gadgets, all talking to each other.
• Power up: No more carrying around a bunch of chargers. Thunderbolt 3 can power up your laptop and gadgets, delivering up to 100 watts in total.
• External graphics and storage: Hook up external graphics cards for gaming or video editing, and super-fast storage devices directly into your laptop with Thunderbolt 3. It's like giving your laptop a turbo boost!
• Backward compatible: Got older USB devices? No problem. Thunderbolt 3 plays nice with them too, ensuring you can still use all your favorite gadgets.
• High-speed networking: Share files at lightning speed between computers with a 10 Gb Ethernet connection over Thunderbolt. Say goodbye to slow network transfers.
• Stay secure: Thunderbolt 3 has built-in security to keep your devices safe from unauthorized access.
• Choose your cable: Whether you need a long cable for convenience (up to 2 meters with active cables) or just a short one for maximum speed at a lower cost (with passive cables), Thunderbolt 3 has you covered.

Thunderbolt 4 introduces several significant upgrades:

• More screen real estate: Thunderbolt 4 supports dual 4K displays or a single 8K display, offering a more immersive visual experience compared to Thunderbolt 3's capabilities.
• More power: It can provide up to 100W of power charging from a single port, catering to more demanding devices and ensuring faster charging times.
• Even faster data transfers: With PCIe data transfer speeds of up to 32 Gbps, Thunderbolt 4 doubles the data throughput of Thunderbolt 3, making file transfers and data access significantly faster.
• Advanced features: The ability to wake a computer from sleep using an external keyboard or mouse connected via a Thunderbolt 4 port adds convenience for users.
• Greater security: Thunderbolt 4 includes Direct Memory Access (DMA) protection, enhancing the security against potential threats by preventing unauthorized access to memory.

On the horizon is Thunderbolt 5, which dramatically improves on Thunderbolt 4:

• Supports USB4 2.0 80 Gbit/s specification
• Doubles the total bandwidth of Thunderbolt 4 to 80 Gbit/s
• Doubles the PCI Express data-throughput to 64 Gbit/s
• Support for DisplayPort 2.1
• Up to 240W of charging power downstream
• Backward compatible with previous versions of Thunderbolt, USB, and DisplayPort

The USB protocol is now almost 30 years old, and has seen numerous updates over the decades. Nowadays we're only concerned with USB 3.2 and USB4, both of which make use of USB-C connectors, although USB 3.2 can also use the older Type-A connectors.

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Since its release in 2019, USB4 has been the protocol of choice because it brings several improvements to the table, partly because it is itself based on the Thunderbolt 3 protocol.

• High performance: USB4 offers data transfer speeds up to 40 Gbps, doubling the maximum throughput of USB 3.2. This is achieved by using a two-lane operation using the USB Type-C connector and cable.
• Compatibility with Thunderbolt 3: One of the most significant aspects of USB4 is its compatibility with Thunderbolt 3 devices and cables, thanks to the underlying technology shared between USB4 and Thunderbolt 3. This ensures a wide range of devices can leverage the high-speed connectivity offered by USB4.
• Multiple protocol support: USB4 supports multiple data and display protocols simultaneously. This means it can handle data transfer (like files and storage), display protocols (such as DisplayPort and HDMI), and power delivery through a single USB Type-C connection. This multi-function capability simplifies the user experience and reduces the need for multiple cables and adapters.
• Backward compatibility: USB4 is backward compatible with USB 3.2, USB 2.0, and Thunderbolt 3, meaning devices and cables supporting these standards can connect to USB4 ports, albeit at their respective speeds and capabilities.
• USB Power Delivery (USB PD) integration: Like its predecessors, USB4 supports USB Power Delivery (USB PD), which allows for power negotiation up to 100W between devices, enabling faster charging and the ability to power larger devices like laptops through a USB connection.

There are Thunderbolt 3 cables, Thunderbolt 4 cables, USB 3.2 cables, USB4 cables, and then an ocean of cheap scabby cables that are everywhere.

If you have Thunderbolt hardware, you need Thunderbolt cables. I recommend getting Thunderbolt 4 cables, since they will be backward compatible with Thunderbolt 3 hardware, as well as anything that uses USB-C ports.

Also: The best USB-C cables for the iPhone 15: What the experts recommend

Yes, they're a bit pricier, but think of it as investing in peace of mind knowing you've got the right tool for the job.

If you don't care as much about compatibility, performance, and reliability, then buying a decent-quality USB-C cable should suffice.

Thunderbolt, by and large, is for professionals who demand the very best from their hardware and are willing to pay whatever it takes for the best possible compatibility, performance, and reliability. These are the people who will be running multiple displays, editing loads of video and photos, and moving massive files to and from external drives.

Everyone else will be fine with USB 3.2 or USB4 hardware, which will be cheaper and more ubiquitous.