How do I know if WINE is installed?

The store says WINE is installed, but I don't see it in my apps, or an option to use WINE to open a .exe file.

You can find installed WINE and WINE-related packages with the following command:

dpkg -l | grep ^ii | grep -i wine

You can find its default prefix with its size by

ls -ld ~/.wine
du -sh ~/.wine/*

and other prefixes (usually created by winetricks) with

ls -ld ~/.local/share/wineprefixes/*
du -sh ~/.local/share/wineprefixes/*

You can use the -s (status) switch of dpkg:

dpkg -s wine

Returns 0 if installed or 1 if the program is not installed.

Another way to see if a package is installed and which version (Installed: [...]). You also see which version would be installed (Candidate: [...]).

apt-cache policy <package name>
apt-cache policy wine

Advantage of apt-cache: You can use wildcards(*) if you don't know the exact package name.

To rightfully see if WINE is installed you should run:

which wine

The which command will either return an exit status of 0 if installed or a 1 if not installed...

To find the exit status of the command, simply run:

echo $?

It is a very simple yet important command to know about...