Reda,
RMG380 and RME180 are two of the ten grades of residual fuel in the ISO 8217 marine fuel standard. They are often called IFO380 and IFO180, with the IFO meaning Intermediate Fuel Oil.
These are the two most popular residual fuel grades, at least 90% of the market, which is why Bunkerworld only shows prices for these two grades.
Other grades, such as IFO120, are rare but might typically meet (or not) the ISO spec but have a viscosity in cst denoted by the number after IFO.
MGO is marine gasoil and MDO is marine diesel oil. Again, the specs for these are set out in ISO 8217 and they are both distillate marine fuel grades.
HSFO is high-sulphur fuel oil and is a generic term covering a number of different fuel oil grades.