Catching a burning or acrid smell after driving is unsettling, and the brakes are a common source. Sometimes it is harmless, sometimes not. Here is what a burning smell after braking means.
Normal on new brakes
Fresh pads give off a slight burning or chemical smell during their first hard stops as they cure and bed in - this is normal and fades after the break-in. Riding the brakes down a long hill can also make a hot-brake smell that clears once they cool; see why brakes get hot.
A dragging brake
A persistent burning smell, especially from one wheel, often means a caliper is stuck and dragging - the constant friction overheats that corner; see sticking caliper and brake drag. You may notice a pull, a hot wheel, or reduced fuel economy along with the smell.
Other burning smells
Do not assume it is always the brakes - a burning smell can also be oil on a hot exhaust, a slipping belt, or a dragging parking brake left partly on. If the smell is one wheel and comes with heat, suspect the brake.
What to do
If new pads, let them bed in and cool. If it persists or comes from one wheel, have the caliper and slides checked before it damages the pad and rotor; see why brakes grind. Fit quality pads and hardware.