A statement is a sentence that tells something.
Use a period(.) at the end of a statement.

The trees are green.

Crabs live underwater.

The balloons are flying in the sky.
A question is a sentence that asks something.
Use a question mark (?) at the end of a question.

Do you like eating popcorn at the movies?

Have you seen an elephant before?

What is hiding in the log?
Remember: All statements and questions begin with a capital letter.