In Italian, some verbs are reflexive, meaning that the person doing the action does it to him or herself. Examples of this would be “mettersi” (to put a piece of clothing on), “chiamarsi” (literally “to call oneself”), and “sentirsi” (to feel). In the dictionary, you may notice that the infinitive has “si” on the end to show the verb is reflexive.
Reflexive verbs have their own pronouns:
io - mi, tu - ti, lui/lei/Lei - si, noi - ci, voi - vi, loro - si
These pronouns match the verb (“mi” with the “io” form, “ti” with “tu,” etc.) and are usually placed before the verb:
Mi metto la giacca. I put on my coat." (from https://www.duolingo.com/skill/it/Clitic-Pronouns-1/tips-and-notes)