This character is a Math Symbol and is commonly used, that is, in no specific script.
The glyph is a subscript version of the glyph Equals Sign. It has no designated width in East Asian texts. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. The word that U+208C forms with similar adjacent characters prevents a line break inside it.
The Wikipedia has the following information about this codepoint:
Unicode has subscripted and superscripted versions of a number of characters including a full set of Arabic numerals. These characters allow any polynomial, chemical and certain other equations to be represented in plain text without using any form of markup like HTML or TeX.
The World Wide Web Consortium and the Unicode Consortium have made recommendations on the choice between using markup and using superscript and subscript characters:
When used in mathematical context (MathML) it is recommended to consistently use style markup for superscripts and subscripts […] However, when super and sub-scripts are to reflect semantic distinctions, it is easier to work with these meanings encoded in text rather than markup, for example, in phonetic or phonemic transcription.