Anno 1404 has a dubious English translation, with many places being seemingly machine translated with spelling, grammar, and formatting errors. So an unofficial patch was created by a user, Brumbek. The goal is to create a truly professional English translation, both for British and American English.
The project expanded and also changed and fixed quite a few broken quests. It also translated about 100 quests into English that never had text before.
It also includes a few mods that can be used without breaking achievements or medals. The mods are such as infinite water for Norias, infinite Natural Resources, no "Production Halted" sounds, and only have one person to find for all "Wanted Person" quests.
So the Unofficial Anno Patch is a hybrid localization, bugfix, and restoration patch. It requires Venice and will have no effect on the base game.
The patch can be downloaded here.