What is a statement in which 2 expressions are equal?

An equation.

So, for example, all of the following are equations:

• 2 = 2
• 2 + 3 = 5
• 2x + 3 = 4y - 7

For comparison, if the statement contains a less-than or greater-than symbol, it is an inequality, even if it also has an equals sign. Here are some examples:

• 2 + 3 < 7
• 2x >= 3y