The restaurant is so popular because of the Krabby Patty, a burger with a very top secret recipe, which has almost always been the signature Krusty Krab dish. Other Krusty Krab grub includes typical fast food products such as French fries and sodas, as well as underwater foods such as "Coral Bits" and "Kelp Rings."
All of these items make up the "Galley Grub", the food menu of the Krusty Krab. The Krusty Krab's employees include SpongeBob as the fry cook and Squidward Tentacles as the cashier.
Unlike Squidward, who hates his job and is terrible at it, SpongeBob loves his job and is great at it. The two employees work great together (according to SpongeBob) and terribly (according to Squidward); Although Squidward hates SpongeBob, this thinks that is one of his best friends. The Krusty Krab's main business competitor is the Chum Bucket, owned by Plankton, Mr. Krabs' worst enemy and former best friend.
While the Chum Bucket, the restaurant's only competitor usually fails, there have been some short times when the Chum Bucket was not failing. These infrequent short periods of time are the only times when the Krusty Krab has any competition.