Can be used from shifting 2V input to 5V output, 5V input to 2V output, and anything in between.
Hysteresis is about 5% of Vout; for a 5V output, this means approximately 250mV hysteresis. If not convinced, use superposition: dVin-/dVout= (100k//100k)/[100k//100k+1M]=50k/1.05M=4.76%.
That hysteresis keeps the circuit from double pulsing for slow or non-monotonic edges on the input; this is critical for fast digital circuits. It is also nice to have an output logic level that can be completely independent from the input logic level.
