Bunny hopping is an exploit that characterizes counter strike from other FPSs actually. It's a glitch that takes practice to use effectively and was never an intended feature of the game. People use scripts and mods to use this glitch more effectively.
In tournament play you are allowed to bunnyhop without scripts. It's harder and less usefull in csgo but still done. Most servers aren't gonna ban you for bunnyhopping unless you are doing nothing but bunnyhopping around the map the entire game. You won't get a vac ban.
You can do it for quite a while with mousewheel = jump (which isn't considered scripting). Doing it effectively / keeping the speed does require practice. Was way easier in 1.6 and source tho.