Surfing the internet I fount this command
$apt-cache search <keyword>
It is helpful to search for packages related to keyword we gave, when we don’t know exact name of package.
apt-cache does not manipulate the state of the system but does provide operations to search and generate interesting output from the package metadata.
Here you are performing a query against the information stored on your local machine for available packages. This is the cache from your “subscribed” repositories. That is, the command is performing a query against the repositories that you have set up in USC(Ubuntu Software Center) or Synaptic.
/etc/apt/sources.list is the location to fetch information from in the query.
$apt-cache search painting
It will return a list of all packages whose name or description contains the keyword “painting”
Similarly try with
$apt-cache search puzzle
It will return a list of all packages whose name or description contains the keyword “puzzle”