Bonus Feature - This is a separate game from the normal slots game that comes up on some machines when you get a certain combination of symbols on the reels. Check the pay table on your machine to see what these symbols need to be. Remember, not all machines have this.
Bonus Games - Bonus games are a lot like bonus features, but they give you free spins on the slot machine instead of a separate game. The same things apply, check the pay table of your machine to see what symbols you need to activate this feature.
Multi Line - These are slots that pay on multiple lines rather then just on the center line like some slot machines do. Each line will normally cost the same as the center line, but this will give you more chances of winning.
Progressive Jackpot - This is jackpot that builds up the more that people play it. These are usually joined to several machines, so anyone playing those machines can win it. These jackpots can be very large, but most do need you to bet big to be in the running.