What are M.A.C.H.O.S ? Give a deatiled introduction.

Massive astrophysical compact halo object, or MACHO, is a general name for any kind of astronomical body that might explain the apparent presence of dark matter in galaxy halos......................................
A MACHO may be detected when it passes in front of or nearly in front of a star and the MACHO's gravity bends the light, causing the star to appear brighter.
MACHOs may sometimes be considered to includeblack holes. Black holes are truly black in that they emit no light and any light shone upon them is absorbed and not reflected. It is thought possible that there is a halo of black holes surrounding the galaxy