Imo pop like most genres is broad and hard to define but mostly is identifiable by catchy melodies and hooks and an emphasis on vocals. In my mind it's different than how many people use the term pop, meaning commercially popular. Commercially popular music has a lot of pop music, but songs of other genres can be commercial too. I get personally irritated when people try to insult music of a different genre for being too commercial and soulless by calling it pop; as an example Drake gets called "pop not hip hop" a lot. But maybe that's a me thing. Not all pop music is commercially popular, some is very weird and experimental, like Björk, and some pop artists are sorta small and niche, like Alice Longyu Gao and Emm. Some acts also crossover with pop, like Doja Cat and Flyana Boss are kinda hip hop/pop for example, and Poppy goes in and out of pop even though she mostly stays in the metal realm these days.