Q:

meta charset = UTF-8 vs charset = iso-8859-1

Why are we specifying charset = "UTF-8" in meta tag?
Is it mandatory to specify this in our web pages?
Does it has any other value other than utf-8?
And what is this iso-8859-1? Please answer where and when should we use them?

A:

UTF-8 
UTF-8 (UCS Transformation Format 8) is the World Wide Web's most common character encoding. UTF-8 is backward-compatible with ASCII and can represent any standard Unicode character. The first 128 UTF-8 characters precisely match the first 128 ASCII characters (numbered 0-127), meaning that existing ASCII text is already valid UTF-8. After the first 128 code points, it utilizes a multibyte approach for additional characters.
ISO-8859-1 
By contrast, ISO-8859-1 is a single-byte encoding scheme. The major downfall of this type of encoding is its inability to accommodate languages that are composed of more than 128 symbols.  
Source: MDN entry on UTF-8

