What is active-trader-pro cask in Homebrew?

Question

Could not find any useful information about it. Also https://formulae.brew.sh/ does not have any cask named as it is.

❯ brew install docker
Running `brew update --auto-update`...
==> Auto-updated Homebrew!
Updated 2 taps (homebrew/core and homebrew/cask).
==> New Casks
active-trader-pro                                              tuist                                                          xtool-creative-space


Warning: Treating docker as a formula. For the cask, use homebrew/cask/docker

Edit: adding brew list

❯ brew list
==> Formulae
aom     docker      imath       libavif     libvmaf     ncurses     pcre        webp        zstd
brotli      giflib      jpeg-turbo  libpng      little-cms2 nvm     sdl2        xz
cmake       highway     jpeg-xl     libtiff     lz4     openexr     sdl2_image  zsh

==> Casks
iterm2          visual-studio-code

Trying to delete those give the same error:

❯ brew uninstall active-trader-pro
Error: Cask 'active-trader-pro' is not installed.

Edit:

Following accepted answer we can check out homebrew docs

Taps (Third-Party Repositories)

The brew tap command adds more repositories to the list of formulae that Homebrew tracks, updates, and installs from. By default, tap assumes that the repositories come from GitHub, but the command isn’t limited to any one location.

Answer 1

It does not mean it's installed on your computer, but rather a new package (software) is added to brew repository.

If you try to install it, you will see it's gonna download https://www.fidelity.com/webcontent/CodeweaverInstaller/ActiveTraderPro.pkg, which is fidelity trading software.