PoGOmap.info is easy to use but really unreliable because the map imagery tiles and the cell overlay are not aligned. Also, most stops and gyms are somewhat inaccurate as that database relies on user entered data where some users are not that thorough with doing it fully correctly.
That’s why people usually recommend to use the IITC and plugin setup instead.
IITC is a modified display of the map in Ingress. As Pokémon GO and Ingress mostly share the same points from Niantics general database, IITC will show Ingress Portals of which a lot are also Stops or Gyms. Together with the pogos2cell plugin, these Portals can be marked with Pokémon GO info manually, but the coordinates will also always be correct, so way less to do.
You can find some explanations for terms you don’t know here: Glossary for Common Wayfarer Terms
And you can also keep asking. Directly spell out which words confuse you