What is Thunderbolt?
Intel introduced the Thunderbolt platform in 2011 at a time when USB 3.0 was all the rage and could transfer data at speeds up to 5Gbps. Thunderbolt was capable of twice that, 10Gbps, plus it could transfer multiple types of data - not just serial data to storage devices.
It could, for instance, pipe video data to displays. It could also daisy-chain devices together, such as your hard drive to your computer and a display to your hard drive. It was the connector of the future, as a single cable (and a single plug) could do it all.
The first two Thunderbolt standards used miniDisplayPort connectors. They did not become very popular, but many MacBook owners should recognize them, as they were a mainstay on Apple's laptops.
The big step forward when it comes to Thunderbolt was Thunderbolt 3. It uses the same design as the familiar USB Type-C connector, making it much more versatile and hardy, but it was also the only connector on Apple's Pro laptops for a few years. It showed that only one port can do it all - even if you sometimes need to use quite a few dongles.
What can Thunderbolt do?
Thunderbolt is so popular nowadays because it allows you to use multiple devices with completely different functions using only one port on your laptop or PC. Because of the wide range of protocols that it supports, you can expect almost everything to work with it - from your regular thumb drive to your external GPU and more.
Here are some of the standards that Thunderbolt supports:
Of course, depending on the Thunderbolt generation, the speeds of these will vary, but having all of those standards contained in a single cable is a huge deal. Plus, Thunderbolt is also backward compatible to sweeten the deal, so you don't have to worry about your accessories not working with a newer laptop or the other way around.
What's the newest Thunderbolt?
Even though Thunderbolt 3 was (so far) probably the biggest step for that technology, it has already been replaced. Right now, the newest standard is Thunderbolt 4, which was introduced in July 2020. It brought some considerable improvements to the platform, but it also kept the old 40 Gbps maximum transfer speed from Thunderbolt 3.
So what does Thunderbolt 4 add? Several useful things:
It increased video data support. Thunderbolt 4 can support a single monitor to 8K resolution or two 4K monitors - doubling the capability of Thunderbolt 3.
Adds a wake-from-sleep function, allowing for a quick start with connected peripherals.
PCIe data speeds have doubled to 32 Gbps. This is handy if you connect an external graphics card to your PC.
It adds security - with VT-d protection restricting direct memory access.
However, the days of Thunderbolt 4 are already nearing their end. Intel already announced Thunderbolt 5 with many new improvements, and we should see machines supporting it, maybe even next year.
Is Thunderbolt 4 just USB4?
The confusion between the name USB and every other cable that uses the same port is quite real. You have DisplayPort cables, Thunderbolt cables, and normal USB cables, all of which use the same plug.
The connector looks the same, being USB Type-C, but Thunderbolt 4 assures you're getting the top-spec USB4.
Because USB4 has various layers: there's a 20Gbps version, for example, despite it being capable of 40Gbps. Thunderbolt 4 ensures that top speed happens.
USB4 also doesn't guarantee the ability to run dual 4K monitors, while there's no mandatory wake-from-sleep requirement - all of which you get with Thunderbolt 4.