What Is an Anagram?

There are different types of anagrams, according to a book I was reading for about 100 years ago. The Amherst Thespians is an anagram of inapt hams use theatre. So the Archbishop of Canterbury is another church's type of rabbi. There's a Guinness World Record for the longest anagram that you can get in the English language. And this is for a non-scientific English word. In the scientific ones, they're pretty bizarre.