Mods are just files that can make your morrowind experience fantastic... or horrible.
When you start getting mods be very careful when installing them on morrowind files, every single file must be in the right place.
Alltough this is easy process, Just Winzip / winrar reguired - The mod files will locate theirselves if you extract them correctly in morrowind data files.
There is endless tutorials and helping sites for morrowind mod installation, these forums are the closest
Before getting mods be sure that the mod is clean (no unecessary things inside, sorry im bad at explaining this)
For further iformation ask fable and the more experienced players.
There is endless types of mods, from new towns, buildings, quests to new islands, landmasses, NPC's, weapons and armors ofcourse
I hope this little gave you some help.