What is Tactical Voting and why is it Practised? -Which Small Parties will go for the Big Parties?

-Tactical Voting is when people vote Against their Best Interests as they know their First Choice has no chance to Win - It would be a Wasted Vote -The Votes go to their Second Interest, or for the Candidate that will Beat the Party they hate most -The Greens may vote for Labour to prevent Conservative -UKIP or Reform UK may go for Conservative preventing Labour