When you say "Thanks" to a person, it is like saying "Thank You" but shorter. "Thank" is actually doing it. For example, I could say, "I need to THANK him for the present."

thank is a verb used to express gratitude thank you for helping me. we thanked her for lending us some money. Thanks is an expression of gratitude A: here is a present for you. B: thanks/thank you. thanks to Sam, we won the match.

"Thank" is a verb. while "Thanks" is a noun. "Thank you" equals to "Thanks" except that "Thanks" is kinda informal

Here is an example: I need to thank you for asking this question, so I will now say thanks!