Science fiction fandom started through the letter column of Hugo Gernsback's magazines. Not only did fans (also called "faans") write comments about the stories — they sent their addresses, and Gernsback published them. Soon, fans were writing letters directly to each other, and meeting in person when they lived close together, or when one of them could manage a trip (travel was harder in the 1930s than it is today).
One of the things that science fiction fandom does is organize science fiction conventions. Some of the largest of these are the Worldcon and DragonCon. Worldcon has been the premier convention in fandom for over half a century; it is at this convention the Hugo Awards are bestowed.
Another major activity is writing for fanzines (see also science fiction fanzines). These amateur publications may or may not discuss science fiction, and are often traded rather than sold. In recent years, websites have largely supplanted printed fanzines as an outlet for expression in fandom, though many popular fanzines continue to be published.
Many professional science fiction authors started their interest in science fiction as fans.
Fandom is responsible for a number of innovations, notably filk.
Fandom includes sub-sets of fans that are principally interested in a single writer or genre: for example, one could talk of 'Star Trek fandom' as an entity. (So much so, that they are better known as "Trekkers" (or "Trekkies") by the rest of fandom).
Notable figures in the history of fandom include: