Do you need to slice loaves of bread? Then you need a bread knife. You can get away without having one of these if you buy your loaves pre-sliced. If you don't, you're going to need a bread knife because the serrated edge is essential for slicing through crust. If you try to cut a loaf of bread with a chef's knife, you will just end up with a bunch of crumbs all over the place and a smashed loaf.
This knife design does have uses other than bread, though. Personally, I prefer using a shorter 8-inch bread knife, because it's helpful for slicing oranges, grapefruit, butternut squash, cantaloupe, and honeydew. The serrated edge is perfect for cutting through the tough rind on different fruits and vegetables the same way that it cuts through bread crust.