- Than is for comparisons
- I am taller than you.
- I like beans more than broccoli.
- Then is temporal or conditional
- Temporal: a sequence of events
- First we went to the mall, then we got lunch.
- Conditional: the old if...then construction
- If you find that the defendant violated the statute, then you must find the defendant negligent.
As you can see, these similar-looking words are distinct from one another in use. All you need to remember, if you are not one who enjoys analyzing grammar, is that than is for comparisons and then is for everything else.
Does this make more sense than before? Good, then.