The equator is 0˚. As you go north of the equator, the latitude increases all the way up to 90˚ at the north pole. If you go south of the equator, the latitutde increases all the way up to 90˚ to the South Pole. In the northern hemisphere the latitude is always given in degrees north and in the southern hemisphere it is given in degrees south.
Longitude works the same way. It is angular distance measured east and west of the Prime Meridian (which has been arbitrarily set at Greenwich, England). The prime meridian is 0 degrees longitude. As you go east from the prime meridian, the longitude increases to 180 degrees. As you go west from the prime meridian longitude increases to 180 degrees. The 180 degree meridian is also known as the international date line. In the eastern hemisphere the longitude is given in degrees east and in the western hemisphere it is given in degrees west.