This is the 286th most frequent Persian word.
کردم
"کردم" means "I did" in English.
Here, 'کردم' is a form of the verb 'کردن' (to do), used in the past tense indicating an action I performed.
من تکالیفم را انجام کردم.
I did my homework.
In 'کرد', a related form is used to describe the action of helping. The addition of 'م' at the end in 'کردم' means 'I' performed the action.
او به من کمک کرد و من واقعاً قدردانم.
He helped me, and I am truly grateful.
Here, 'کردم' describes the organizing act ('کردن') finalized for my tasks in the first-person past tense.