Matching pitch is the act of reproducing with your voice the pitch of a tone you hear. It is the most basic and most important ear training skill, and is therefore the starting point for virtually all ear training. You don't need to have a great singing voice, but you do need to be able to get the pitch or frequency of the tone right, without singing it too sharp or too flat.
When you hear somebody sing who is consistently way out of tune, it is usually because they have never mastered this basic skill. The term 'tone deaf' is often used to describe people who attempt to sing a melody without first having acquired the ability to match pitch. True 'tone deafness' is extremely rare, but off-key singing is surprisingly common. This can be improved considerably through ear training and practice.