A "long-term" goal is a goal that someone plans to achieve several years in the future. Usually we think of a long-term goal as something that will happen in about 2-15 years.
Here's an example:
Do you have a specific long-term goal that you're working toward?
Of course, you can also talk about a "short-term goal", which is something you want to accomplish in a few weeks or in a year or two.