They are used to locate a certain place on a map.
Latitude and Longitude
The system of latitudes and longitudes is a method used to locate points on the Earth's surface. There is a similar coordinate system used to locate objects in the sky, but it's not latitude/longitude.
Yes.
Yes.
The lines of latitude provide vertical (north-south) coordinates on a map or globe. Lines of longitude provide horizontal (east-west) coordinates. The defined geographical point is where the latitude line intersects the longitude line.
To locate any spot on the Earth's surface.
By Longitude, Latitude, minutes, seconds. Or use Google Earth.
"Longitude" and "latitude" are the coordinates used primarily in the system of locating points on the earth's surface. Even when that generalization doesn't hold, they're only applicable to the location of points on the surface of another sphere. There's no way to use that kind of system to locate a planet.
It is like coordinates all around the earth
Every point on Earth has a latitude and a longitude. No two points have the same set of two numbers.
The equator is the locus of all points on Earth whose latitude is zero. The locus of all points on Earth whose longitude is zero is the Prime Meridian.
The Prime Meridian is a line made up of all the points on Earth that have zero longitude. There is one of those points at every possible latitude.