How to check if a package exists in Debian?

Question

linux

There is a debconf package https://packages.debian.org/ru/wheezy/debconf it has perl-base dependencies
There is perl-base https://packages.debian.org/ru/wheezy/perl-base it has dependencies dpkg
There is dpkg https://packages.debian.org/ru/wheezy/dpkg it has a lot of packages in its dependencies
Questions:
1) How to check if there is a package in the system
2) If I need debconf, install each package of dependencies and its dependencies separately il Is there any way to wholesale everything?

Answer 1

in general, that is dpkg -l | grep
i.e. dpkg -l lists all installed packages
grep (package name) filters it.