"Chanting" means that the words--often the words of a prayer--are "intoned," meaning they are sung on a single, sustained, musical note, in order to communicate something about obedience to God, or induce some kind of meditative or devotional mood. The purpose is not to entertain an audience. There are only a small number different notes. The tune is not supposed to be musically interesting, but to echo the style of other chants. Chants are often described as "hypnotic," and people now make collections of chants to be played as aids to sleep! "Chanting" is also used to describe the musical delivery made by children or political protesters who are trying to mock or make angry fun of somebody or something. In "singing" the words are sung to a musically interesting tune, often as entertainment. The best way to understand is to listen to some examples. This is a Catholic prayer known as the "Ave Maria." Here it is chanted: https://www.youtube.com/watch?v=3Tc0rkd39qQ Here it is sung, to music composed by Schubert: https://www.youtube.com/watch?v=sE1WoMocTlw

Chanting is normally singing something for a ritual purpose of some kind. It is not usually meant as entertainment, art, or self-expression. Chanting often is not something anyone would enjoy listening to. It may contain only a very basic rhythm and repeat the same tone with no variation. Most people would not even call that singing.