What is a "sidestep landing" in an instrument approach?
From the AIM 5-4-19:


  5−4−19. Side−step Maneuver  
  
  a. ATC may authorize a standard instrument approach procedure which serves either one of parallel runways that are separated by
  1,200 feet or less followed by a straight−in landing on the adjacent
  runway.  
  
  b. Aircraft that will execute a side−step maneuver will be
  cleared for a specified approach procedure and landing on the adjacent
  parallel runway. Example, “cleared ILS runway 7 left approach,
  side−step to runway 7 right.” Pilots are expected to commence the
  side−step maneuver as soon as possible after the runway or runway
  environment is in sight. Compliance with minimum altitudes associated
  with stepdown fixes is expected even after the side−step maneuver is
  initiated.  
  
  NOTE−
  Side−step minima are flown to a Minimum Descent
  Altitude (MDA) regardless of the approach authorized.   
  
  c. Landing
  minimums to the adjacent runway will be based on nonprecision criteria
  and therefore higher than the precision minimums to the primary
  runway, but will normally be lower than the published circling
  minimums.