If you play two notes at a time, they will be connected by an orange line. If you play three or more notes at a time, they will form an orange shape. These geometric visualizations are meant to support and complement your aural understanding of intervals and chords, the way that they do with rhythms on the Groove Pizza.
Initially, musicians used 808s on their own as the kick. While you can definitely still do that, things have progressed. Nowadays, the subby 808s are most commonly found as a bass tone that’s been layered with a punchy kick sound. This punchier kick layer typically has less bass content and is there to help create a crisper attack. At its most basic, the kick and 808 play essentially the same pattern, but the 808 bass provides the sub and tonal content.