Essentially, an ISOT involves taking a large area of land, say an island or a country, and sending it back or forward in time to another era. This usually also results in the land from that time being sent back to 'now' to replace that country, but this is not necessarily part of the definition.
For example, a scenario with the premise of “2006 Germany ISOTed to 1942” would mean that the territory of 2006 Germany replaces that of 1942 Germany. This would serve as a set up for a story, where the ISOTed 2006 Germany and the rest of the 1942-Earth have to react to this strange event and to each other's presence. Coping with the ensuing culture shock and various differences would also be a major issue, especially early on in the story. Incidentally, this kind of “coping with the aftermath of an ISOT” is a very common theme (or trope) in works that use it.
However, ISOT has become such a popular term that it is now often used simply in lieu of 'time travel', of one person, such as 'ISOT myself to WW1'. ISOT is primarily now used as a verb, though also as a noun.
ISOT is usually pronounced as 'eye-sot'.
Over the years, AH.com has had some rather philosophical discussions about the details of the whole ISOT concept.
One of the most frequent types of debates was “What happens to the country/territory that gets replaced by the time-displaced country/territory ?”. Generally, there are two “schools of thought” concerning this issue. Using an ISOTed France as an example, these two schools are :
The first idea is generally popular and is also generally assumed to be the “default solution” of any scenario involving an ISOT. The second idea is less popular, but has its proponents and fans.
Many published AH works are based on the premise of an ISOT.
This includes the aforementioned Island in the Sea of Time trilogy by Stirling, but also Eric Flint's 163X series, Harry Turtledove's The Misplaced Legion, John Birmingham's Axis of Time trilogy and Without Warning series.
However, note that the actual term/acronym 'ISOT' is rarely used in published fiction. The authors usually prefer to pick their own naming conventions. For instance, in the 163X books, it is termed 'The Ring of Fire', and in the Island in the See of Time itself, it is referred to simply as 'the Event'.
Many ASB timelines and stories created on AH.com are based around various types of ISOTs.
Some notable examples from the New Board's early years :
Max's First Law - A theoretical postulate dealing with the general results of an ISOT.