theres 2 basic types of suspension you can buy.
TRUE coilovers, which are "one piece" and have both a spring and a shock built into one another as one piece. tein, jic, silkraod, tanabe, etc fit into this category
the other more common and cheaper option is seperate springs and seperate shocks, buitl togehter using some of your stock pieces, top hats, and so forth to replace your stock pieces. slip-over coilovers fit into this category as well. such as ground control, skunk2, etc. springs like eibach intrax, and so forth fit here, along with normal shocks, like kyb agx's, koni yellows, and tociko blues, to name a few of the common ones.