mods are improvements or modifications to the game for example you could get all the items (called the too many items mod)but on survival. mods arnet only inanimate items , you can get another place like another world or you could get mobs like horses.
texture packs are modifications to the game where it ghanges the look of the objects in the game from default to something else some texture packs are built to make minecraft run faster on slow computersso it isnt that choppy but the blocks may be harder to tell apart
the mods and texture packs can be found on the minecraft website