Base64 - encoding an array of bytes 64 using ASCII characters. The characters used are A-Z, a-z, 0-9, +, /. Every 3 bytes are encoded with 4 characters.
First, 3 characters (24 bits) are taken and divided by 4 numbers of 6 bits each. These numbers are indices for the string 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'. If less than 3 characters are used, the remaining characters are padded with '='.
Hellow World = SGVsbG93IFdvcmxk
It was beautiful = SXQgd2FzIGJlYXV0aWZ1bA==