coil over kits vs spring and strut

Whats the difference between a coil over kit and just buying struts and springs? Im new to those parts so i have no idea. Any help would be great. Also, which would be best to use?

Struts/Springs are sometimes have adjustable dampening, but usually not too much. My boys IS300 has Tokoyos on them and are 5-way adjustable with a 1.5"-1.75" drop. I have coilovers, and they're 32-way adjustable, 0"-4" drop, and can adjust spring rate. Spring/shocks are great if you get good sets, and usually have a decent price to them. Coilovers are more race-ready, and cost a lot of money.

so if i were to buy coil overs would i have to buy struts also or anything else?

Depends. Coilover sleeves require struts, which you have to modify. Coilover kits come complete, but cost BIG $$$ for a proper (matched, dyno'd, etc) set. The budget coilovers you'll come across (800-1k) are generally acceptable for street duty, but don't see the same QC as the high end kits and DIY kits.

Stock struts are not meant to be operated at ride heights other than stock. If you use stock struts with any lowering springs they will blow out relatively quick so its not recommended.