This character is a Uppercase Letter and is mainly used in the Greek script. Its lowercase variant is Glyph for U+03B3Greek Small Letter Gamma. The character is also known as gamma function.
The glyph is not a composition. Its width in East Asian texts is determined by its context. It can be displayed wide or narrow. In bidirectional text it is written from left to right. When changing direction it is not mirrored. The word that U+0393 forms with similar adjacent characters prevents a line break inside it. The glyph can be confused with 15 other glyphs.
The Wikipedia has the following information about this codepoint:
Gamma (; uppercase Γ, lowercase γ; Greek: γάμμαgámma) is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. In Ancient Greek, the letter gamma represented a voiced velar stop IPA:[ɡ]. In Modern Greek, this letter normally represents a voiced velar fricative IPA:[ɣ], except before either of the two front vowels (/e/, /i/), where it represents a voiced palatal fricative IPA:[ʝ]; while /g/ in foreign words is instead commonly transcribed as γκ).
In the International Phonetic Alphabet and other modern Latin-alphabet based phonetic notations, it represents the voiced velar fricative.