High-Velocity Clouds (HVCs) deviate from the "normal" galactic rotation (VLSR > 100 km s-1).
Compact HVCs (CHVCs) are a sub-class of HVCs. They are compact (<2°), isolated in position and velocity from the galactic HI emission (Braun & Burton 1999)
Blitz et al. (1999) proposed that CHVCs can be considered as the "Building Blocks" of the local group galaxies.