This finds every material whose molecule contains a particular structural fragment — a ketone, a macrocyclic ring, a substitution pattern — written as a SMARTS query. The presets are a starting point: each one loads the pattern behind a structural class we already index, and you can edit it from there.
SMARTS is the pattern language RDKit reads — roughly SMILES with wildcards. Nothing is sent anywhere: the matching runs in this browser.
Matching runs over the 2 materials with a recorded structure. Naturals and other mixtures carry no single structure, so they are never matched.