A domestic airport is an airport that mainly handles domestic flights. Because of the nature of the operations, usually there are no customs or immigration and duty free services. The passengers travel only from/to airports in the same country so no complicated services and procedures are required.
Domestic airports tent to be much smaller than International airports and designed to handle fewer people, aircraft and cargo per day compared to larger international airports. There are exceptions like those in Canada and US of America, which have more traffic than half of Africa’s airports put together. But mainly the rule is that domestic airports handle small aircraft and short to medium haul jets. The runway also tends to be smaller. A casual trend is 1200meters to 2400 meters runway and no taxiway, so backtrack is required. Domestic airports can run 24/7, but you might also find them open for just 2 hours per day in order to provide services to a single flight.
The facilities nowadays are the same, since the requirements for safety are the same for international airports and domestic airports. Of course the nature of the airport dictates that fewer checks have to be made, but never the less security levels are high corresponding to the number of passengers traveling. Smaller airports mean less walking for the passengers but also more crammed seats and secondary facilities.
Most 80`s domestic airport have boomed commercially and can`t expand any more. Those airports are chocking with passengers eager to travel and have fallen behind or failed completely on upgrading, in order to serve all these passengers. Also many domestic airports today have upgraded their facilities to international standards even though they don`t have international routes in their schedule.
Domestic airports tend to be a life line for certain regions of countries where usage of other types of vehicles like trains and cars are not economically viable or not accessible. These airports help local communities sustain a constant supply chain or grow their tourism and offer a fast and comfy form of transportation. Great examples of those types of airports can be found on Mountain ranges like Nepal’s and South Americas and the domestic airports serving the Greek islands.
Some international airports have dedicated domestic terminals but those airports can’t be classified as domestic since they also serve international routes.