Sports simulations are a particular breed of play-by-mail (or play-by-e-mail) games which concern themselves with the management of a fictional sports team or fictional individual in a sport like tennis or boxing. The most commonly simulated sports are American (gridiron) football, soccer (Association football), and hockey, though someone's had a go at just about any team sport, not to mention a fair number of individual sports. Generally, participants in these games send in instructions to the moderator (frequently referred to as a "commissioner") who processes the instructions using either a special computer program or a board game and reports the results back to the participants. Players also take on the role of managers, trading players amongst themselves and issuing "press releases" tweaking the opposition. Games which are played through postal mail are generally fee-based, to cover the cost of stamps if nothing else. Games played via e-mail are usually free but some charge for turns.