It mostly used in the music field, and it means if a person sings in a correct frequency. Well, even though I'm a huge music fan, and I listen to songs from South African Mp3 Download really often, but I can't really tell whether a person sings on pitch or not, I just decide whether I like how it sounds or not. Maybe that's the way people define it, but to be honest, I'm not really sure about that, it depends on notes, after all.
In music pitch means the perception of the frequency of a particular note. Pitch is often considered to be one of the most fundamental aspects in the world of music.
Alternatively if a person is singing or playing off pitch it means they are singing or playing false. This is not very easily rectified.
In order to sing on pitch a person can try the following easy steps. Play the notes in order in a particular musical scale. Do this without singing and listen very carefully. Then try to visualise yourself singing this same note. Practise this several times and then try singing. Experts generally find that people who sing off pitch usually never listen to the notes.