Into and onto are used with verbs to show movement - for example: The boys ran into the lake. Jack threw his bag onto the chair. In and on can be used with or without a verb of movement. They are used to show place or position, for example: The pencils are in your bag. The books are on the desk. I hope this helps:D

'Into' is in+to. Ex. I walked into the house (ie. I walked to the inside of the house). 'Onto' is on+to. Ex. I climbed onto the roof (ie. I climbed to the top of (on) the roof.)