As you have seen in previous grades, an expression is a mathematical statement that uses numbers, variables, and operations to show a relationship between certain quantities.
These are all examples of expressions that you may have seen.
If two expressions are equal, then the resulting mathematical sentence is an equation. These are examples of equations that you may have seen.
Because the two expressions on each side of the equation are equal, you will see the metaphor of a balanced scale used to represent the two sides of the equation.
For example, the equation 5 = 3 + 2 is shown in the image below using a balanced scale.