"What's the difference between "likely" and "registered" voters? Is it that "likely" may not be "registered," and, if they're not "registered," why bother to ask them? They can't vote unless they're registered. what am I missing here?"
The point is -- often times these "polls" are just surveys of people, some or most of whom don't vote or are not even registered to vote.
"what am I missing here?" "Likely voters" are registered voters who say they will vote on election day. "Registered voters" are just those who are registered, but there is no indication of their intention to vote. Truth be told, polls of "likely voters" are considered more accurate.