A conditional statement is an if-then statement. For every conditional statement you can write three related statements, the converse, the inverse, and the contrapositive. The video shows how these are related.
If you can write a true statement using "if and only if" , then you've got a biconditional. Learn more about biconditionals by watching the video.
When a conditional statement and its converse are both true, you can write them as one statement called a biconditional statement. Learn more about this special kind of statement by following along with this tutorial.