A retinue (Old French retenue, from retenir also meaning 'to employ', from Latin retenere, hold back, retain) is a body of persons "retained" in the service of a noble or royal personage, a suite (literal French meanings: what follows) of "retainers."
Some were a source of trouble and abuse in the 15th and early 16th century (see maintenance). Often their real importance was very different from their rank: on the one hand sinecures and supernumerary appointments allowed enjoying benefits without performing full service, on the other hand 'having the ear' of the master can allow to act as a confident in an informal capacity, in some cases even as a spy in such an at first sight innocent functions as a musician.
For example a Prince's entourage would not only include professonial courtiers, but also various bishops, clerics and other clerks, senior members of the aristocracy and other more occasional advisers, translators etcetera, who would often not be part of a Sovereign's (more permanent) retinue, even though that could comprise a surprising variety of functions, from menial to lofty.