As P G points out the single equals is the assignment operator, while the double equals is the equality operator. You can sort of think of a variable like a box where we're going to store a value. When we use the single equals sign we're saying what's going to go in that box:

x = 5

In this case we have a "box"(variable) named x and we're putting the value 5 inside of it. We're not asking it... we're telling it. But when we use the double equals it's a comparison operator. And this works more like a question:

if (x == 10)

Here, we're asking is the value currently in the box labeled x 10? No, it's not... it's 5. Hope this helps clear up the equals signs!