As we mentioned, local scope refers to something declared inside a VBA procedure. A variable with local scope is invisible to code in any other procedure. Module-level scope refers to a variable declared in an Access module but outside of any procedure. For example, if you have several procedures that work with a Recordset, you can declare the Recordset variable outside of any of the procedures and then refer to it inside any of them. You can declare a module-level variable using the Dim keyword.
Global scope is probably the easiest to understand.
Something with global scope is visible everywhere in your program. In Access you make something global by declaring it in a code module using the Public keyword. There's quite a bit more to know about scope, but that's enough to get you started. Let's wrap up with two general rules. In a large program it's easy to end up with code that changes a global variable in ways that you didn't expect.