What is the meaning of ?

Indicates items in a list that are fulfilled or dealt with, e.g., products in a grocery list that were already bought.

Indicates one's preference or vote. Sometimes, a ballot () can be filled with a checkmark: .

Indicates correctness (with the exception of some languages, in which it is used with the opposite meaning). See also: (indicates wrongness).

Used as a tally mark.

ISO 2047 symbol for Acknowledge.

Source: wiktionary.org