The particle 'se'

QuestionAnswer
Ana is washing her face
Ana pere lice
In English you have certain words that require a subject (The thing in a sentence the action is being done to) because without it, the sentence is left ambiguous. If you were to just say 'Ana is holding', the sentence would sound weird because it doesn't nearly have enough information, What is Ana holding? You cant hold nothing so there needs to be a subject. In Serbo-Croatian there are significantly more verbs that require a subject: brijati (shave), buditi (awaken), oblačiti (put on clothes), prati (wash)...
He is washing a shirt
On pere majcu
Ana is washing (herself)
Ana se pere
If the person or thing in the sentence is doing an action that requires a subject, then the particle 'se' is used, it means 'self' and isn't pronoun specific (myself, yourself, himself, herself, itself, ourselves, yourselves, themselves)
I'm shaving
Brijem se
I'm not shaving
Ne brijem se
I almost never shave
Skoro nikad se ne brijem
Skoro se nikad ne brijem (also correct)
Ana is dressing
Ana se oblači
Oblačiti se - to dress
I'm waking up
Budim se
buditi se - to wake up
She's returning a book
Ona vraća knjigu
She is returning
Ona se vraća
vraćati se - to return
My name is Ege
Zovem se Ege
Zvati se - to be named
I'm having fun
Zabavljam se
zabavljati se - to entertain
The window opens
Prozor se otvara
If something is being done to the word in a sentence without anything or anyone doing it being mentioned, then you also use 'se'. Literally translated the example sentence would be 'The window opens itself'
The soup is cooking
Supa se kuha
Kuhati se - to cook (the soup is cooking itself)
The meat is cooking
Meso se peče
Btw even though something is technically being done to the subject you don't change it to accusative, this is because its taking the role of the action doer
He's playing
On se igra
We are laughing
Smijemo se
Smijati se - to laugh
I'm not having fun
Ne zabavljam se
You shave every day
briješ se svaki dan
The soup is cooling
Supa se hladi