This is a pretty basic question that most IT managers ask candidates when it comes to cryptology. If you have any level of expertise with encryption, you should be able to answer this question without too much difficulty.

The reason a hiring manager will ask this question is to get one or two easy questions out of the way, then proceed to more difficult questions. Keep in mind that some managers tend to drill down into this question pretty deep so if you get asked, be prepared to answer with a detailed response.

The basics here are going to be that symmetric uses a single key, and a public key uses two keys. Let's suppose that you took a document and placed it in a drawer, then locked it with a key. If anyone else wanted to access that document, they would need a key for that drawer. This is how Symmetric key encryption works. A public key, on the other hand, would require two keys to open up a drawer.