What is a patch?
A patch fixes problems that prevent the proper execution of software. It is a collection of files and directories that replace or update existing files/binaries and directories.
The entire OS is installed as a collection of Solaris packages. It is done during the OS installation via the pkgadd command. Patches are build in a similar fashion. Patches are partial packages which replace files in the existing packages then they update the pkg/patch databases.
Some patches only update one package in the OS others update several packages. To get an idea as to which packages might be updated by a patch look into the patch directory itself. There will be at least one sub-directory of a package which will be updated. Full Story