10. What are the differences between one-way and two-way systems ?

One-way systems use dialup telephone lines for upstream traffic, and the satellite connection for downstream. What that means is, lower latency (good) and lower upload speed (bad). You also need to tie up your phone line while you are on the Internet.

Two-way systems use the satellite for both downstream and upstream traffic, allowing for better throughput. You don't need to tie up the telephone line. The only downside is, you add considerable latency to the equation because upstream traffic must travel up to the satellite and down to its destination on earth again (240ms+ delay).