How do I know if my hair is dead/damaged or unhealthy etc...?

(I'm female btw)

Idk much about hair but recently I've noticed some groups of strands of hair are shorter than others and during showers when I brush hair comes out. I also have no idea what "bad" hair looks like. I don't have straight hair. I don't know what dead ends are or anything. I feel lost when it comes to hair and I don't have a woman to help me with my hair. If anyone can shed some help I'd be happy. I'm a minor so I can't purchase things when I want or but special things.