'Motet' is a term used to define a type of choral composition. Throughout time, the term has described different types of choral pieces. It is believed that motets first appeared during the 13th century from certain sequences in liturgical music. The practice of discant over a cantus firmus became the basis for counterpoint in academic Western musical tradition, and from this practice arose the first medieval secular motets. These were compositions for several voices, usually employing different texts in vernacular languages (sometimes more than one language), sung over a cantus firmus adopted from a Gregorian chant.
In the late Middle Ages the isorhythmic motet was the norm: repetitive rhythmic patterns were used throughout all the voices. A complex style arose eventually, with the cantus firmus being extended to great lengths, its rhythmic variations no longer evident.
During the Renaisance the motet came to be redifined as we know it today. It consisted of a choral polyphonic setting in Latin, sometimes employing imitative counterpoint. The texts used were, in general, was not particular to any liturgical moment, and therefore usable in any service. The motet came to be a form very similar to the madrigal: in fact, many argue that the main difference between motets and madrigals during the Renaissance is merely the purpose of their composition and the language they employ (motets being written in Latin, madrigals in vernacular languages). Of course there were also secular motets and sacred madrigals, blurring the limits of these forms even more.