What is scaffold / Medicinal chemist feeling #memo

Recently I’m interested in the following article. https://pubs.acs.org/doi/abs/10.1021/acs.jcim.0c00204 The author tried to detect chemical series (scaffold) like medicinal chemist. In the drug discovery project chemical series / scaffold is very important concept to analyze compounds SAR but it is fuzzy. As chemoinformatitian know Bemis-Murcko scaffold is one of the solution for systemic detection of chemical series