How is 'lion' not greater than 'zebra'? In the example he used in the video he used 'apple' is > (some b word).

You are misremembering the video. In the video the example provided was 'apple' < 'bear', so the < (less than) operator was used, not the > (greater than) operator.

When you compare strings to each other letters later in the alphabet will be considered greater than those that comes before. So 'A' is less than 'B', 'C' is less than 'D' and so on.

It's also worth noting that capital letters are considered to be lesser than non-capitalized letters. So 'a' is actually greater than 'B'.

With strings, "greater than" means "comes later in the alphabet". So "zebra" is "greater than" "lion".

You may have incorrectly recalled the video example, I believe you're referring to the point where he points out that "apple" is less than "bear".