Vvardenfell is a large island located in Morrowind's Inner Sea.

"Vvardenfell, also called the Black Isle, is a large island located inside the bay-like Inner Sea, and is surrounded by mainland Morrowind with the exception of its northern coast, which meets the Sea of Ghosts. The island is dominated by the great volcano, Red Mountain. The island itself is named after the original Dwemeri name of Red Mountain, literally translating to "City of the Strong Shield". It is characterized by arid wastes, rocky highlands and coastal wetlands filled with unusual and unique flora and fauna."

Biscuit_290 wrote: »

Is the former a part of the latter or vice versa? Searching for each one on the web got me the same map; now I'm more confused than ever.
If it's only a portion, then how do I see the rest of the area? I have the base game with morrowind.

Also, once I buy the summerset, elseweyr etc. DLCs, will I be able to walk across borders or will I need to do something like teleportation and go to another map entirely?

Morrowind is a province (kind of like a real-life country) within Tamriel (the continent), and Vvardenfell is a large island within Morrowind.

Online searches will bring up a map of the same area because the game Morrowind (TES III) and the ESO expansion called Morrowind were both set on Vvardenfell, so the search is showing you the map for the game or expansion, not the whole province. In real-world terms the fact that other areas are also part of the province is usually irrelevant.

Kind of like how England is just one part of the United Kingdom, but a lot of people use the two interchangably, because it's the biggest and probably best known bit.

You can see some of the rest of Morrowind in-game. The base game maps Bal Foyen, Stonefalls and Deshaan are all part of Morrowind. Other parts of the province are currently inaccessible: the small area between The Rift and the sea and the long peninsula which goes north from Deshaan and east of Vvardenfell. These areas might be added in future DLC or expansions, but we don't know for sure, or when that will be.