From OpenCog

The IdenticalLink is a kind of virtual link that evaluates to true when its two arguments are the same atom. If not, it evaluates to false. IdenticalLink is used to test for syntactic equality, that is, for identity. To test if two atoms are semantically equal (identical after having been executed), use EqualLink.

The primary use of IdenticalLink is during pattern matching, when one or both of its arguments contain variables to be grounded. Thus, when the pattern matcher grounds the variables with actual values, the IdenticalLink can be evaluated to see if identity holds or not (with the pattern match being accepted or rejected as a result).

IdenticalLinks can be combined with AndLink, NotLink and OrLink to create arbitrarily evaluatable crisp-logic boolean expressions.

They can be evaluated with the cog-evaluate! function.

See also