Latitude
Latitude is the number of degrees of the Earth's surface that a point is situated either North or South of the Earth's equator. The equator itself is a 0 degrees latitude, and the North and South poles are at 90 degrees North (plus) and South (minus) of the equator, respectively.

Longitude
Longitude is the number of degrees of the Earth's surface that a point is situated either East or West of the Prime Meridian (otherwise known as the Greenwich Meridian). The meridian itself is at 0 degrees, and on the other side of the earth is the International Date Line at 180 degrees East and West. Values East of the Prime Meridian are given positive (plus) longitude values, and values West are negative (minus).

Degree format
Each degree of latitude and longitude is divided into 60  minutes, and each minute into 60 seconds. A latitude is often shown as 52°22'20"N, meaning 52 degrees, 22 minutes and 20 seconds North of the equator, with a corresponding longitude like 4°52'58"W, meaning 4 degrees, 52 minutes and 58 seconds West of the Prime Meridian.

To simplify matters, degree values are often shown using decimals. So, a latitude of 52.3723 is the same as 52°22'20"N, and a longitude of -4.883 is the same as 4°52'58"W.