An expression is like a puzzle you have to solve, just like how you might put together a puzzle with different pieces.
In math, expressions are made up of numbers, signs, and sometimes letters. You have to figure out what the expression means by putting the pieces together in the right way.
For example, if you see the expression "3 + 5," that means you have to add the numbers 3 and 5 together to get a total, which is 8.
Sometimes, expressions have parentheses or brackets around them, like "(2+4) x 3." This means you have to solve the expression inside the parentheses first (2+4, which equals 6), and then multiply that answer by the number outside the parentheses (3), which gives you a final answer of 18.
So, think of expressions like a fun challenge to solve, just like putting together a puzzle!