Logic is about being able to apply the principles of reasoning to an argument or situation. In maths, this is generally limited to abstract concepts like numbers, functions and shapes, but the principles of logic can be applied everywhere. See if you are a logical thinker in this GCSE Maths quiz.
Another way to understand logic is to think of it as the correct rearrangement of facts to find the information we want. When you think of it in these terms, hopefully you can see that, for instance, a properly laid out solution to solving an equation is an application of logic. If we combine two number facts, it is logic that helps us to understand the outcome. For instance, if I add 2 positive numbers together, it is logical for the sum to be bigger than either of my original numbers.
Being able to think logically is a valuable skill to have, regardless of subjects studied or prospective career-paths. In court, lawyers and judges apply logical reasoning to facts, to decide if a person is guilty or innocent. A good debater can take a bunch of facts and apply them logically to support their argument, regardless of whether they actually agree with it or not!