Here are some helpful videos to review the concept of Latitude and Longitude. In these videos you will learn more about projections, datums , and coordinate systems. Review these if you are struggling with these concepts at all, as they are the fundamentals of all spatial data and analysis.
Map Projections and the Earth (3 min)
Map Projections, Latitude, and Longitude (Stop at 7:45)
Map Projections and GIS (1 min)
Map Projections: A Video Lecture (8.5 min)
A Simple Explanation of Datum (2 min)
Geographic Coordinate System (8 min)
Projected Coordinate System (10 min)