depends, there are about 20 different encryption options.
let's start with the basics - what PRODUCT did you put on the endpoint - Endpoint for File/Folders, or Endpoint for PC.
the former is file encryption, so you'd have to set a policy to encrypt that directory. The latter is a FDE product, so if the partition is encrypted, then everything stored on that partition is encrypted.
a bit vague, but the chances are that if you chose to encrypt a drive, and you have some indication this occurred, then the files on that drive are protected. You might want to ask whoever runs this project in your organisation.
I am also trying to find the answer to this so I can put together an FAQ for my directors. Many of our staff also use offline files. We've purchased Endpoint Encryption. How will this affect offline files when they re-connect to the network, will they be encrypted on the network as well?