The cost of medieval manuscript paper ensured that the majority of written work was religious in nature. This in turn meant that the common language used was Latin. However there are exceptions and there are secular works in the local vernacular.
Interestingly, a lot of the work is anonymous. It has been presumed that there was such awe for classical writers and this combined with the power of the church would encourage anonymity.
Religious texts - Catholic clerics were the dominant intellectuals of the time and it is their literature which see most often. Many of the texts were theological or philosophical texts discussing the great debates and heresies.
The mystery plays grew out of re enactments of biblical scenes and these grew to be very popular. Secular texts - the best known of these come from the concept of courtly love and the poem songs of the Troubadours.
Travel stories were very popular and where these crossed over with religion you got pilgrimages and epics such as Chaucer's Canterbury Tales.
It is also worth mentioning the role of allegory in the medieval ages. The most influential example of this is probably Dante's Divine Comedy.