From the aptitude man page :
As a special case, “install” with no arguments will act on any stored/pending actions.
In other words, you tried to install those packages earlier (or they were brought as dependencies), yet something went wrong (or the process was interrupted) and it couldn't finish.
aptitude is just trying to finish what it started. The operations may also concern updates, package removals or any kind of internal, pending operation.
Another interesting man page excerpt you might want to know about :
Once you enter Y at the final confirmation prompt, the “install” command will modify aptitude's stored information about what actions to perform. Therefore, if you issue (e.g.) the command “aptitude install foo bar” and then abort the installation once aptitude has started downloading and installing packages, you will need to run “aptitude remove foo bar” to cancel that order.
In other words, if those packages are of no interest to you, calling
remove for them might purge the pending operations queue (the aptitude's stored information).