It depends entirely on the type of bread. Soda bread/biscuits/etc. can be as simple as mix and bake, but yeast breads usually require multiple steps over the course of a couple of hours. Usually something along the lines of:

1. Mix ingredients
2. Knead thoroughly for several minutes
3. Let rise for ~1 hour
4. Press the dough flat again and knead again
5. Let rise again
6. Bake
7. Let cool

The intermittent rise periods are what allows the loaf to expand and gives the center its fluffy texture. It's not a terribly difficult process, just requires intermittent attention over a fairly long period of time. You may have heard talk about bakers starting their job very early in the morning; people traditionally wanted fresh bread in the morning, and it takes several hours to actually make (even if most of that time is just waiting), so bakers need to start several hours early.

A bread maker turns the long process into basically just "put in all the ingredients and press go". It still takes a while, but doesn't require any attention once it's started. You can also just put the stuff in at night and have it start on a timer so it's ready in the morning.