Where to find this information in the system

You can find this information out in the head of dpkg -l output, as it's just a formatting convention:

dpkg -l | head -3

Copied here for reference:

Desired=Unknown/Install/Remove/Purge/Hold                                     
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)                    

Description of each field

As you can see from the first three lines:

First letter -> desired package state ("selection state"):

• u ... unknown
• i ... install
• r ... remove/deinstall
• p ... purge (remove including config files)
• h ... hold

Second letter -> current package state:

• n ... not-installed
• i ... installed
• c ... config-files (only the config files are installed)
• U ... unpacked
• F ... half-configured (configuration failed for some reason)
• h ... half-installed (installation failed for some reason)
• W ... triggers-awaited (package is waiting for a trigger from another package)
• t ... triggers-pending (package has been triggered)

Third letter -> error state (you normally shouldn't see a third letter, but a space, instead):

• R ... reinst-required (package broken, reinstallation required)