Adjectives can take one of three nifty forms:
Positive. For when you don't want to make or imply a comparison.
Comparative. For when you want to compare two things.
Superlative. For when you want to compare three or more things.
Here's a nifty table with some examples:
"As far as movies go, The Texas Chainsaw Massacre is totally unsuitable for children."
In this bloody good example, unsuitable is a positive adjective. That's because no direct comparison is being made here; unsuitable simply describes the 1974 slasher flick about a chainsaw-brandishing killer.
"Crocodiles are meaner than alligators."
There are several ways to distinguish crocs from gators. Crocodiles have long, V-shaped snouts and dig saltwater. Conversely, your average alligator has a wider, U-shaped snout and attends the University of Florida. But this sentence is all about comparing how mean the two animals are, which makes meaner a comparative adjective.
"Blitzen is the fastest of all of Santa's reindeer."
In this sentence, fastest is a superlative adjective because it's comparing all eight of Saint Nick's reindeer—or nine, if you count Rudolph. He's a fairly recent addition to Santa's sled-pulling platoon, created in 1939 by Robert L. May for Christmas coloring books given away by Montgomery Ward. Before May settled on Rudolph, he briefly considered naming him Rollo or Reginald. But whatever his name, he's definitely not the fastest.