To impede something is to delay or block its progress or movement. Carrying six heavy bags will impede your progress if you're trying to walk across town in a hurry.
Impede comes from the Latin impedire which literally means "to hold the feet," formed from the prefix in-, ("in") plus pes ("foot"). Think about walking with a cast on your foot — how slow and awkward that would be. If you struggle with reading, that might impede your progress in your social studies class. An impediment is something that impedes, such as a physical defect that affects speech — a speech impediment.