what is a KEY?!?!

i'm so confused.

before I learnt the basics of formal music theory, and before I learnt I had perfect pitch, I used to categorize songs into "vibes".

i later on realized that each vibe was a note in the western notation. the 12 notes.

i then learnt scales, major, minor, etc.

and I realised each vibe was infact a minor scale to me. if I felt like a song was in the "key" of F#, it was in F# minor.

i realised most of the music i listened to was minor music and not major.

i'm confused as to what a key is. to me, it's still the "vibe, the "home" of a song.

some songs now, I can't make out the key of properly.

ex, Paradise City by Guns N Roses. someone please help me out. this song feels like it's F# minor to me, but not exaclty. more like it's constantly revolving around F# minor and would finally resolve into it. but it's always playing "around" F# minor.