You use a hammer drill, pneumatic hammer drill, or an SDS drill when you want to drill in very hard materials, such as concrete. If a hammer drill has a rotation stop, it's called a combi hammer. You can also use it to chisel tiles from the wall. Most hammer drills are corded, but there are also cordless SDS drills. That means you can easily work in places without a socket. How large the holes you drill are, depends on the impact power. Want to drill holes with a 5mm to 22mm diameter. A 3J impact power is enough.