This image is a reference to things like this, where you send dry (containing low water content) solvent through a column of activated alumina to make it even more dry.

It doesn’t really work as well with some solvents. The one I used in grad school had DCM, toluene, THF, and acetonitrile. If we needed dry DMSO, DMF, DMAc, acetone, MEK, or alcohols they had to come from a sealed bottle.