Why the texture is there
Concrete straight off a float is smooth, and once it is wet that smooth surface is close to slick. Dragging a broom across it while it is still soft cuts a pattern of shallow lines into the top skin. Those lines break a sheet of water into channels instead of leaving a solid film to stand on, which is the difference between a driveway you can walk on in a downpour and one you cannot.
It is not a decorative choice so much as a working one. The same texture that helps a bare foot on a wet patio helps a tire find grip on a wet or icy driveway, which is why broom finish is the standard on almost every outdoor slab, not an upgrade.
Where it lands in the pour
Brooming comes near the end of the sequence, not the start. The crew screeds the concrete level, bull floats it to knock down high spots and bring paste to the surface, then waits. Broom too early and the bristles drag through soft concrete and leave ragged furrows instead of clean lines. Broom too late and the surface has already started to set, so the broom skates across the top without cutting in at all.
That window is short, especially on a warm afternoon, and it does not open at the same moment across a whole driveway. A finish crew works a slab end to end, edging and jointing the first section while the far end is still being floated, so each part gets broomed at the right stage instead of on one fixed schedule. On a pumped pour concrete keeps arriving at a steady rate, which is part of what lets the crew hold that pace evenly instead of racing a truck that dumped the whole load at once.
Coarse or fine, and which direction the broom runs
A stiff push broom pulled straight across a driveway leaves a coarser texture, the kind that still grips a tire when there is snow or ice on top of it. A softer bristle broom, or the same broom drawn lighter, leaves a finer texture that still sheds water but feels less rough under bare feet, which is the more common pick on a patio or a pool deck walk.
Direction matters as much as bristle stiffness. Running the broom across the narrow dimension of a driveway, rather than down its full length, keeps the lines consistent and keeps the crew from having to stand on a section they still need to finish.