A legislator makes laws. Congress is full of legislators. You have several who represent you at both the state and national level.
Don't confuse a legislator with the legislature. Whereas the latter refers to the group such as the Congress, a legislator is a member of the group. At the national level, senators and representatives are given the task of writing our laws. States sometimes have different names for their two legislative houses, but the set-up is similar. The United States may be the world's oldest democracy, but legislators have been around nearly forever — the Romans had them.