Alliances (factions), completely separate areas, except for the PVP zone?

In Elder Scrolls Online, I started my character in the Ebonheart alliance. Now I'm level 20 and have visited into neighbouring areas out of curiosity, discovering level 48 characters and similar. By neighbouring areas I am still talking about the areas in the Ebonheart alliance, up to the right in the global map.

Does this mean that the areas I play in now, around Morrowind, for the Ebonheart alliance, is completely separate from the two other alliances?

In other words, are there 3 completely separate areas, and the only place I will meet characters from the other 2 alliances is in the PVP zone?

Or do I need to travel to one of the other areas in time to further level up and continue playing?

Solution 1:

You are correct, the only time you will "meet" other factions is in Cyrodiil. Once you have completed the main story and reached Veteran rank 1, you will be given the option to play the Daggerfall covenant or Alderi Dominion quest lines. Even then you will be phased with other Ebonheart Pact players and see no other factions.