vacuum truck or vacuum tanker is a tank truck that has a pump and a tank. The pump is designed to pneumatically suck liquids, sludges, slurries, or the like from a location (often underground) into the tank of the truck. The objective is to enable transport of the liquid material via road to another location. Vacuum trucks transport the collected material to a treatment or disposal site, for example a sewage treatment plant.
A common material to be transport is septage (or more broadly: fecal sludge) which is human excreta mixed with water, e.g. from septic tanks and pit latrines. They also transport sewage sludge, industrial liquids, or slurries from animal waste from livestock facilities with pens.
Vacuum trucks can be equipped with a high pressure pump if they are used to clean out sewers from sand.
2- Other names used for vacuum trucks: vacuum tanker, "Sucker truck" (in Australia) or "Sewer Sucker", "Hydro-vac", or "vac-trucks" (in Canada) or "Exhauster truck" (in Rwanda, Malawi). Slang terms include: "honey truck", "honey sucker" (in India and South Africa), and "honeywagon", all (probably) derived from honey bucket.
When a vacuum truck is used to transport fecal sludge then it can also be called "fecal sludge truck".