If it says to evaluate an expression, does it mean to answer it?

Evaluating an expression means either to solve the expressions or to simply it.

Solving an expression:

2 - (10 + 5)

A simply expression. After doing the math the answer comes out as -3.

2x + 3x

This is an algebraic expression. This means we have variables like x and y.
 In this case, we can only simplify it. Because we don't know what x is equal to.

Because they are like terms (which means they have the variable) we can add them to together.

2x + 3x = 5x

I hope this answer clears up any misunderstandings about expressions and over all helped you learn something! If you still need some help, don't hesitate to DM on ! I wish you best of luck on your journey of math!

EDIT:

Now what if you have an expression like this:

5x + 5m where x=4 and m=8

In mathematics, something like 5x is the same difference as 5 * x.
And x is just a placeholder for a number or for another variable.

And in this equation, x is equal to 4. So, we just replace x with 4.

5(4) + 5m

Same this with m. The variable m is equal to 8.

5(4) + 5(8)

We can solve!

5(4) + 5(8) = 20 + 40 = 60

Our answer is 60.