(Pocket-lint) - The ports on the side of your laptop are important. They decide what you can do on your device and how quickly you can do it.

In 2018 when Apple introduced a new style MacBook Pro, it ditched every single port of its old machines and replaced it with just Thunderbolt 3. Many PCs makers followed suit. Now it's fairly normal to have at least one USB-C/Thunderbolt 3 port on a device.

What is Thunderbolt 3?

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.

USB 4 is now on the way, which will include the Thunderbolt 3 specification within it. In other words, all USB 4.x ports will be Thunderbolt capable to deliver the same speed and features.

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Thunderbolt 3 uses the same design as the familiar USB Type-C connector. This connector is used for simplicity foremost, but there are other reasons, too.

Early versions of Thunderbolt relied on a Mini DisplayPort-style connector, and Apple was the only major manufacturer to embrace Thunderbolt. But hardly any laptops used or would use Mini DisplayPort and, with USB-C coming to the fore and in many ways replacing Mini DisplayPort, it made perfect sense.

Thunderbolt 3 supports the DisplayPort protocol too, so you can use one cable to daisy-chain and drive multiple 4K displays at 60Hz.

Thunderbolt 3 allows for connection speeds up to 40Gbps - so double the speed of the previous generation - USB 3.1 10Gbps, and DisplayPort 1.2.

It also offers USB speeds of up to 10Gbps, and it can connect up to two 4K displays, outputting video and audio signal at the same time.

It also supports DisplayPort 1.2, HDMI 2.0, and 10GbE fast networking.

Plus, Thunderbolt 3 is backwards compatible.

So what is USB-C?

USB Type-C - or USB-C for short - is a physical USB connector. It's replaced Micro-USB connectors previously used by most Android phones and will eventually even replace USB Type-A, which is the standard larger scale USB connector that everyone probably thinks of when they hear "USB". 

The previously-mentioned USB 4 specification will still use the USB-C connector. 

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USB Type-C is well-known because it allows for quicker data transfer. By default, USB Type C offers 7.5W and 15W transmissions, whereas USB 3.0 offers 4.5W transmission. USB Type-C also allows your devices to charge, because it can transmit up to 100W, which is enough to charge most laptops.

That means you can use a single cable with a USB Type-C connector to quickly transfer data to your device while you charge it.

But the most interesting thing about USB-C is that the connector is reversible: there is no "right way up". You can just blindly stick it into a port on a device, and it'll smoothly go in and work.

Why are more laptops using Thunderbolt?

Manufacturers have embraced Thunderbolt because of its features - mostly the fast data transfer for storing large files. The fact it uses the now-common USB-C connector is a welcome bonus. 

You can use it to connect your Mac or PC to displays, transfer data quickly between computers and hard drives, daisy chain external devices, and power up - all with just one physical connection.

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Remember that not all USB Type-C ports support Thunderbolt 3 though. While smartphones and tablets may use the connector, it doesn't necessarily mean those top speeds and features are available.

Originally the Thunderbolt platform was only available on devices with Intel processors, but that's since change as Intel shared the technology as part of USB4. That's why Apple's M1 Mac products, which don't use Intel processors, support Thunderbolt, for example.

So, while you can technically plug any USB Type-C device or cable into a Thunderbolt 3 port, it won't support Thunderbolt's features. And a Thunderbolt 3 peripheral plugged into a regular USB Type-C port won't support Thunderbolt features either.

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What about Thunderbolt 4?

Yes, it was inevitable, Thunderbolt 4 succeeded Thunderbolt 3. However, it doesn't offer faster speeds - it's still 40Gbps maximum - and the USB Type-C connector port is still the same.

So what does Thunderbolt 4 add? A number of useful things.

First, and perhaps most important, is increased video data support. Thunderbolt 4 can support a single monitor to 8K resolution, or two 4K monitors - doubling the capability of Thunderbolt 3.

Second, there's wake from sleep, allowing quick start with connected peripherals.

Third, PCIe data speeds have doubled to 32Gbps. This is handy if you connect, say, an external graphics card to your PC,

Last up there's added security - with VT-d protection restricting direct memory access.

Is Thunderbolt 4 just USB4?

The connector looks the same, being USB Type-C, but Thunderbolt 4 is assurance that 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.

Writing by Maggie Tillman and Dan Grabham. Editing by Mike Lowe.