meaning of fetishize

i don't really know what fetishizing mean so i searched it on google but i was too dumb and stupid to understand, so i'll ask here.

does fetishizing mean like you jerk off to something? or whenever you think about it you get horny? or when you see it you jerk off in private? like you are reading something smexy and you got horny? then jerk it off? i also seen this question everywhere so i'll ask, the question was like "is ok to fetishize a porn manga?"

i'm just asking cause i'm curious, so pls tell me if you know!!!