Chords compared side-by-side can help give an understanding of the how different chord types relate to one another, as well as how the chord naming works.
Options can be configured to show different perspectives on each chord type, and the visual for each chord can be clicked to hear the sound of this chord. All chords are starting from the same root to give a better understanding of the musical qualities of each. This tool works best on a large screen, though you can scroll left and right to view this on smaller screens as well.
The 'Include unknowns for scale' option will show all chords for the given root and scale for that same root and scale. Selecting C as the root and major as the scale, for instance, will show all C "something" (major, minor, etc) chords that are also in the key of C major. This will also show every other chord possibility that works in C major, even if it isn't named or known to the system.
For more details on what things you might find here and how to use this, see my writeup on comparing chords using this tool on substack.
Custom Tuning