The USB connector has come a long way from its beginnings in 1995. Over time, there have been several standards that differ from each other, particularly by transmission rates.
This is the oldest USB connector that will still be encountered. Its predecessor, the USB 1.0 is not longer used because, among other things, its slow speeds. It was only 12 Mbit/s, while the maximum theoretical USB 2.0 transfer rate is 480 Mbit/s.
USB 2.0 was launched in 2000 and is now being replaced by newer standards, but you can still plug a USB 3.0 cable into a USB 2.0. You will be limited by the older baud rate.
The USB 3.0 generation (later renamed USB 3.1 Gen1) was introduced in 2008, but it expanded significantly in the course of 2013. Compared to USB 2.0, it increases transmission speeds to 5 Gbit/s. It has the same shape (type A), so USB 3.0 is backward compatible with USB 2.0. From its predecessor, the connector is easily recognizable. The plastic part inside the connectors is blue, while in the case of USB 2.0 it is black.
The USB 3.1 Gen2 is the latest generation to replace older models. It supports speeds of up to 10 Gbit/s, so 10GB of data can be transferred in just 8 seconds. This standard is often found on a USB-C type that is symmetrical. Unlike their predecessors, they have a different shape and are no longer compatible with them. If you want to use it, it is necessary to reach the crossover or reduction.
The USB 3.1 Gen2 standard has a significant user advantage. You no longer need to think about which way is up, because it's completely reversible. So you won't have any problems connecting your phone in the dark.
In addition to different generations, USB connectors also differ in shape or type. They are divided into males (outward connection) and females (receive connection). Here are the most common types of standard sizes: