When do you use the preposition "onto"?

Question

Thank you.

Answer 1

"Onto"= a place or position on; upon; on.

“Onto” and “on to” are often interchangeable, but not always. Consider the effect created by wrongly using “onto” in the following sentence when “on to” is meant: “We’re having hors d’oeuvres in the garden, and for dinner moving onto the house.” If the “on” is part of an expression like “moving on” it can’t be shoved together with a “to” that just happens to follow it.

She got onto a horse.

The dog jumped onto the chair.

The responsibility fell onto his shoulders.

The restaurant adds the tip onto the bill

Answer 2

when you might otherwise say "upon."

George dropped the feather onto her lap.