This section is from the book "The Steward's Handbook And Guide To Party Catering", by Jessup Whitehead. Also available from Amazon: Larousse Gastronomique.
A bun is a sweet roll, raised with yeast like ordinary bread, though there are at least a score of different names, shapes and qualities, and quite a number of people follow the Scotch fashion of calling all sorts of soft rolls, French rolls,peiilspains, rusks or whatever else buns, whether sweet or not, which tends to a confusion of names. However, as said above, buns are sweet rolls not so rich as cakes, and one of the best is the Hot, Cross Bun, specially made for Good Friday and eaten by some people for the sake of keeping up an old custom, and by more because the buns are good. A good bun can be made by any person by taking light bread dough and working into it some butter, sugar, spice or extracts, raisins, currants and candied peel, and yolks of eggs. The fruit is not always put in, and not essential, nor need there be much of either of the other ingredients; it is essential, however, to have good, lively, well-raised dough. The buns are but balls of the sweetened dough set to rise, then baked and egged and sugared over. If to be "cross buns," the cross is made by pushing down a knife nearly to the bottom of each bun while it is rising, when about half light.
Other kinds of buns can be found described under the proper letters.