Help me identify musical genres?

I think something is wrong with my ears, but I love music. To me, it's
either good music, or bad music. My problem is, when I listen to a
song, I have no clue if it's "Alternative", or "Alt Rock", or
"Post-Grunge", or "Indie Rock" or "Punk Pop." How do people
distinguish?

I go by the lines that, if it has enough guitar, it's alternative. If
it's on the radio, it's either Pop, or hip hop. If there's
synthesizers, it's electronic. That's all I can really tell.