The primary data format is geographic coordinates. While thinking of "what is geocoding?" you'll firstly recall this type. It is simply latitude and longitude values that define a specific spot on the map. You've probably skipped learning the coordinate system at school, but you still should understand it well for coding.
There are different standardized systems, but many can be applied equally. The most popular is the WGS 1984. In the US, a North American Datum has reached the highest popularity. For other countries, you can find specified systems. There are no crucial differences between them, and you can apply any of these variants that fit your region.
Also, projected coordinate systems exist. The worldwide system is called UTM, and the American one is called State Plane. You ought to understand a coordinate system properly to work with them. Otherwise, you won't be able to place data on the map in the proper order and convert northing and easting into lat/long format.Example:
Input: UTM Easting – 510500, UTM Northing – 7042500.
Output: Latitude – 63.510617 deg, or 63 deg 30 min 38.2212 sec, Longitude – 9.210989 deg, or 9 deg 12 min 39.56 sec.
Read this explaining article
and learn more about coordinate systems and discover which one will be more comfortable for you.