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.
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 have a hard time reading, that will impeded your progress in math. An impediment is something that impedes, such as a physical defect that affects speech––a speech impediment.