To impede means to slow something down or block its progress. When heavy snow impedes traffic, cars and buses move slower than usual or get stuck. When a fallen tree impedes a hiking trail, you have to find another way around it or clear the obstacle before continuing.

The word suggests something getting in the way of normal movement or progress. A broken arm might impede your ability to play basketball. Dense fog can impede a pilot's vision. Long lines at the cafeteria can impede students from getting to recess on time. An impediment is the thing doing the blocking: the snowstorm, the fallen tree, the broken arm, or the fog.

Notice that impede doesn't mean stopping something completely, just making it harder or slower. You can still make progress when something impedes you, but it takes more effort or time. A student with a speech impediment can still communicate, though certain sounds might come out differently. When you impede someone's work by interrupting them constantly, they can still finish, but it takes longer than it should.