The Drunken Lizard Pub

What's a difference between a new global map and a new savegame map?

I made a new global map. but I don't know how to link the map though. I tried but it seems unsuccessful

The difference is in how they get loaded.

Global maps you place in a "mods" directory in the same location as your datapak file. They must be named in such a way as to connect to one of the unused locations in the game - Fandugan, the teleporter in Rockhammer, Western Mirkland, etc. They can safely be added to any existing game. They can only use "official" items that came with the game. This is the officially supported way to make mods, but as far as I know I'm the only one who released a mod in this format.

Savegame maps you place in your saved game folder, and they can overwrite existing maps as well as creating new ones - see for example the Alchemist's Tower mod, which makes changes to the Moonrise map. However, you can't always add these mods to existing games without "resetting" maps. This format allows you to specify item properties directly, which means you can create items that weren't in the original game.

Does that answer your question?