What is the meaning of ?

Used by writers and proof readers to indicate that something is missing.

Separates the base and exponent in a power expression.

Bitwise exclusive disjunction.

Control key.

Indicates an ASCII control character in caret notation.

Matches the start position within the string. Compare $, which matches the end position within the string.

Used with square brackets: [ ]. Matches a single character other than the characters and ranges specified between the square brackets.

Used to point to a message (or other content) situated above in a forum, chat, etc.

up (in any sense)

Replacing the letter sequence 'up' within a word.

A letter of the Chiwere alphabet, written in the Latin script.

Source: wiktionary.org