|Neko Sakura art|
Neko (猫), it the Japanese for for "cat". On its own, this word has little to do with anime.
The word neko can also refer to cat girls, human girls showing cat-like features. Usually, this only means cute ears and a tail, but occasionally can be taken further. The girl in question can also have pointed teeth or say "nya", which is the Japanese equivalent of meow.
Cat girls also have a male counterpart, but they are fairly rare. Cat girls are more popular than cat boys, and the only one I can name off the top of my head is Ikuto from Shugo Chara! I'm not sure why this is so, but I don't think it's a very popular niche in otome games, either.
Neko are not to be confused with other hybrid types. Ears and a tail do not make a neko, only cat-like features.