Encoding is the process of transforming a set of Unicode characters into a sequence of bytes. In contrast, decoding is the process of transforming a sequence of encoded bytes into a set of Unicode characters. For information about the Unicode Transformation Formats (UTFs) and other encodings supported by Encoding, see Character Encoding in the .NET Framework.
Note that Encoding is intended to operate on Unicode characters instead of arbitrary binary data, such as byte arrays. If you must encode arbitrary binary data into text, you should use a protocol such as uuencode, which is implemented by methods such as Convert.ToBase64CharArray.