apt-cache

 1. Search for a package:

`apt-cache search <package>`

For example:

`apt-cache search apache2`

2. Show details of a package:

`apt-cache show <package>`

For example:

`apt-cache show apache2`

3. Show dependency information of a package:

`apt-cache depends <package>`

For example:

`apt-cache depends apache2`

4. Show reverse dependency information of a package:

`apt-cache rdepends <package>`

For example:

`apt-cache rdepends apache2`

5. Show a list of all installed packages:

`apt-cache pkgnames`

6. Show the version information of a package:

`apt-cache policy <package>`

For example:

`apt-cache policy apache2`

7. Show the size of a package:

`apt-cache showpkg <package> | grep -i "^size:"`

For example:

`apt-cache showpkg apache2 | grep -i "^size:"`

8. Show the total installed size of a package:

`apt-cache show <package> | grep -i "^installed-size:"`

For example:

`apt-cache show apache2 | grep -i "^installed-size:"`