mongoliod its the scientific name for the asian races, it stems from "mongol" others use the term oriental to define the asian peoples.
negroid, comming from negro, which means black, is the term for people of african descent.
caucasian originates from the causcus mountains.

while most scientist will argue that all peope fit into one of the 3 catergories, some say there is a 4th race the "australiod" for the aborriginal peopes of australia and surrounding areas. all other races and country types are sub-groups of the 3 main ones. eg japanese, korean and chinese are mongoliods/orientals. russian, canadian and german are caucasian etc. the ones who wouldnt fit into a particular space would be the mix people, or happas. which i think is alot of central and south america, where the most of the people now are a mix of the original natives (oriental) and the incomming caucasians from spain and the rest of europe.