Difference between on and onto.

I have just watched a grammar book and I do not understand what it means.

Here are what the book writes:

On can be used for both position and movement.

Onto can be used when there is movement incolving a change of level.

Thanks in advance.
There's a box on the floor. Please help me [to] lift it onto the table.

In the first sentence, the "on" describes the position of the box. There is no movement.

In the second sentence, the "onto" describes the movement, or change of position from a low level to a higher one.

That package you're carrying looks heavy. Why don't you just place it on the table?

This action describes movement, but there is no indication that there's a change in level.

The table may be at the same level at which the person is carrying the package.

As an aside, my own opinion is that "onto" can also be used in certain cases in which there's no change in level.

Help me move this table onto the patio.

He pulled the car onto the freeway.
Thank you. ^^