LinkPatterns[link] gives a list of the patterns for which definitions were set up when the external program associated with the specified MathLink connection was installed.
Each element of the list returned by LinkPatterns is wrapped in HoldForm to prevent evaluation.
The patterns in LinkPatterns typically originate in :Pattern: specifications in the MathLink templates used to create source code for the external program.
Uninstall[link] calls Unset on the patterns in LinkPatterns[link].
See The Mathematica Book: Section 2.12.3.
See also: Install.