You can stop a meeting few ways:

When the host presses the red phone receiver to end the meeting, he gets a popup that looks something like this:

If the host checks the "Stop the meeting after you exit", all the participants leave the room, the meeting is over for them. 

If the host doesn't check the "Stop the meeting after you exit", but clicks "Exit" instead, then host rights are transferred to any of the participants randomly.

The meeting will stop up in five minutes automatically on the condition that everyone leaves the room. Or the person who has been rendered host's rights to (moderator) can stop the meeting himself.

If a participant wants to leave, he should push the red receiver button and click "Confirm" after: