The primary difference between USB 2.0 and USB 3.0 lies in speed and bandwidth. USB 3.0 offers significantly faster file transfers and greater power delivery, making it ideal for high-performance devices like SSDs and 4K webcams. Visually, USB 3.0 ports are often blue, while USB 2.0 ports are typically black or white.

In terms of raw speed, USB 2.0 tops out at 480 Mbps, with real-world transfers around 20-40 MB/s. First-generation USB 3.0 can reach 5 Gbps, with average transfer speeds of 300-500 MB/s. USB 3.0 also provides more power, up to 4.5 watts, compared to USB 2.0's 2.5 watts.

USB 2.0 remains relevant for peripherals like mice and keyboards, which don't require high bandwidth or power. These devices work perfectly fine in USB 2.0 ports, and using USB 3.0 ports for them offers little benefit. Conversely, plugging a USB 3.0 device into a USB 2.0 port will bottleneck its performance, limiting speeds to the slower standard.

Both USB standards are backward compatible, meaning USB 2.0 devices can plug into USB 3.0 ports and vice versa. However, to maximize performance, it's best to reserve USB 3.0 ports for bandwidth-intensive devices.