Encrypted Files Extensions - What are encrypted files and how do I open a encrypted file?

What are encrypted files and how do I open a encrypted file?

File Type Category File Format
.axx Encrypted Files AxCrypt Encrypted File
.cng Encrypted Files CryptoNG Encrypted Archive
.e4a Encrypted Files Encrypt4all Archive
.hbx Encrypted Files BinHex Encoded File
.hqx Encrypted Files BinHex 4.0 Encoded File
.mse Encrypted Files 3ds Max Encrypted MAXScript File