A recreationist participates in, or contributes to a reconstruction or re-creation of the clothing, music, skills, activities and lifestyle of a different time period to the current one. This may entail the study of a certain culture or historical period. For example: the Middle Ages in Europe or the Gulf War in the Middle East.
For the most part recreationists only cover situations, "as they should have been", without events that aren't much fun, such as the Black Death. Sometimes this includes a fantastical element, as some include activities or practises that simply did not occur.
Sometimes the term recreationist and re-enactor are used interchangably. Often, a recreationist refers to one who participates in activities like the SCA which have more emphasis on the spirit of the times they recreate. A re-enactor can be considered someone involved in a much more accurate portrayal of the times, and usually has a very specific time and place in history.
Recreationists differ from professionals in that recreationists do it for fun, while professionals get paid for their work.