Where connections, typically between flights, leave little margin (such as close to Minimum Connection Times between terminals).
This tag is used for questions about avoiding the chances of a mis-connect on a short connection, strategies to speed your passage from one flight to another, special provisions at specific airports, risks of luggage not making it, and regulations governing support/assistance given if you miss the onward flight.
When airlines sell tickets with a connection, they have set MCTs (Minimum Connection Times), which vary between airports, between terminals, and sometimes even by flight numbers. The MCT is the shortest connection the airline feels happy offering, and the shortest one it expects many people to be able to make.
Anything at, or just above the MCT, is considered a short connection, often called a tight connection by travellers. On these, there's a risk of a mis-connect.
On a single ticket, if you miss your connection on a short connection, you will be re-accommodated on the next available flight. However, that may not be for a long time, especially during busy periods, so short connections should be avoided if you're connecting onto an infrequent service! Also, depending on the country and the reason for the missed connection, you may well have to fund your own food and hotels while you wait for the new flight.
Airlines may often put additional or special tags onto luggage where you have a short connection, often labelled things like "express connection" or "short transfer" or the like, to help baggage handlers to prioritise those bags. The effectiveness of these can vary though... Where customers need to re-clear security, or pass through immigration, airlines may offer special passes and/or lanes to use, often labelled "express connection" or "short transfer" or "short connection" or the like. Availability and usefulness of these does vary between airlines and terminals.
This all applies on a single ticket. If you have booked two different tickets, and are changing between tickets during the connection, do not book a short connection! In almost all cases, if the first flight is late, it'll be your problem that you missed the second flight. Unless you are sure that the airline(s) offer mis-connect protection between two tickets, only book two-ticket connections well above the MCT.