dot plots detail
Dot plots are often used when visualizing multiple genes/isoforms over groups of cells (or other labels provided by the study creators). This dot plot is created by searching more than 1 genes (S100b Glt1d1 Lmx1b Gabarapl2 Tmem119 Cx3cr1 Cd68 Pdgfra Olig1 Mbp Mog Sox10) in the study from Brain MD70. (You can search these genes yourself in the explore tab of the study).
These plots show both the magnitude of expression (eg. average expression over the group) and prevalence (eg. proportion of cells expressing the gene/isoform) of the gene's activity. These summaries combined help give an overview of sparse measurements like single-cell transcriptomics.