The reflexive pronoun exists also in English, but it is rare : it's the form oneself, myself, yourself etc. In Spanish it is very frequent. The Spanish equivalent of many English verbs are reflexive verbs : I am washing the child - Lavo al niño. I am washing - Me lavo.
Like in English, the reflexive pronoun changes according to the person. Before the verb, it's form is se. In an independent form, used after the prepositions. it's sí (himself, herself, itself, themselves). In conjunction with the infinitive, gerund, and imperative, the reflexive pronoun stands after the verb and is spelled together: lavarse, lávese.

Reflexive pronoun with a verb:

me lavo - I wash

te lavas - you wash

se lava - he/she/it washes

nos lavamos - we wash

os laváis - you wash

se lavan - they wash