we all may know that a simple structure of an English sentence, say " I like apples", would be Subject(S)+Verb(V)+Object(O) meaning that linguistically the structure is called SVO, this is a generative rule enabaling the learners to generate thousands of the same sentences and accelerate their learning.
What about a Persian sentence structure? well, a simple sentence in Persian is of SOV structure:
example: "man Ali raa didam"(=I saw Ali)(من علی را دیدم)
About(را) "raa"(aa is pronounced like a in father, long a): raa doesn`t have any meaning in Persian, it`s simply object marker, meaning that it accompanies the Object in the sentence.Especially with our Direct Object.So, we can say that" Ali raa" simply means "Ali", raa is just there to be with our Object, and specify it.
Good Luck with Your Persian,