We use a period (.) at the end of a declarative or imperative sentence.
We also use a period (.) after an initial in a name and an abbreviation.
I am going to Mexico City next month.
I have music practice at 4:00 P.M. everyday after school.
I shared my book with my brother, J.D. Banks.
We use a question mark (?) at the end of an interrogative sentence.
Have you seen my socks?
How do I get to Fisherman's Wharf?
What do you want to be when you grow up?
We use an exclamation mark (!) at the end of an exclamatory sentence to show strong feelings.
I love chocolate cake!
It's finally summer vacation!
We won the soccer game!