Legacy drivers are just old or outdated drivers. For example, if you get an error message about using a legacy driver, it may be because you are using a Windows 2000 driver on Windows XP. If that's the case, check and see if the manufacturer of your device has an upadted driver.

So, does that mean that I don't need to have those drivers on my computer???

Correct. In fact, for optimal performance, you don't want any legacy drivers installed, but sometimes it's inevitable.

It really depends on what the device is really. Most of the time it's fine. Updating the drivers can cause issues or maybe make things better. If the system works fine with them then leave it alone!!
Cheers
Opus