Used as a verb, you bump into something when you hit it, but not especially hard. You might bump your knee on your coffee table if you are walking around your living room in the dark.
As a noun, a bump is a raised, slightly rounded area on something else. The stone pillar in the picture has a lot of bumps carved into it.
Bis forBun (food)
Bis forBun (hair)
A burden is a heavy load someone is carrying. A burden may be a physical one, such as the load the man in the picture is carrying, or it may be an emotional burden.
You can use burden as a verb too, for example, "he burdened her with his secrets".