Web Acceleration is a transparent HTTP (but not HTTPS) proxy system. One part lives on your modem and the other part is over the satellite link. When you request a webpage, the remote side pre-fetches images and other objects, compresses things as best it can, and then sends them in a big burst to the modem, which makes the web page feel more responsive.
Occasionally, you’ll come across a site that won’t load with Web Acceleration enabled, or will only load partially. You’ll even come across websites that have banned “your” IP address. (In actuality, the IP address of the proxy you happen to be sharing with someone who was banned!) Fortunately, Web Acceleration can be turned off in the modem’s System Control Center.
You’ll want to turn it off when playing online games on your game console.
It’s perfectly fine to keep it turned off. It may make your connection faster at the expense of longer page loads the first time you visit a website. Note that you’ll have to turn it back off each time the modem reboots.