A medium freehand stroke with square ends, like a felt-tip on a print.
The Marker draws a freehand stroke with square-cut ends, the way a felt-tip marks a printed sheet. It sits between the Pen and the Highlighter: heavy enough to read across a room, solid enough to write with.
Draw it: press, drag, release. The cursor is a circle sized to the stroke.
For a wash of colour over an area, the Highlighter starts at width 20 in translucent yellow, already set up for the job the Marker has to be dialled back to do.