je me fiche
as I understand this means "I don't care" but fiche means "plug". can somebody explain?
The same word can have several meanings. Ficher is a colloquial verb synonymous for mettre (to put) Example: "fichez-moi ça dehors".
A more rude variant exists, also beginning with f (as in va te faire fXXXXX)
A more polite way to say "I don't care" would be ça m'est égal (similar to German: es ist mir egal)
The verb is «s'en ficher » and is followed by «de » p.ex «Je m'en fiche de mon travail/ I don't care about my work ». It is in common usage and as others have explained cannot be translated word for word.
It should not be confused with «s'en foutre de .. » which has a similar but stronger meaning. («Je m'en fous de ça/I don't give a damn about that » - or even stronger «va te faire foutre/f*** off » ).