Variable text + expression

Hello everyone. How do I set a text variable to the value of a text + the current year?

You could use an expression:

concat("The year is: ", formatDate(now(), "YYYY"))

Thank you very much. Is there a place where you can find all the functions that you can use as an expression?
If I wanted to add to the text that you have also indicated the value of a variable I must add it in braces or squares?

If you click the link in my post above, it takes you to the main help article for expressions.