London Gatwick Airport (LGW)

Gatwick is one of the busiest airports in the world with only one runway.
London Gatwick Airport has two terminals. The South Terminal, which opened in 1958 with a then revolutionary design of using enclosed piers and North Terminal which opened in the 1980s. Since then a few enlargements have been carried out, mostly new piers to allow for the increase in passengers. Since January 2017 the North Terminal is used for all EasyJet flights while the South Terminal is used for British Airways and Virgin Atlantic flights. Both terminals are connected by a 1.2 km long elevated, automated, mono-rail shuttle train.

The Gatwick Airport is located about 50 km south of London.

Gatwick Airport is located 50 km from London city center so getting to and from the airport can take some time. You have various options though and prices vary a lot.
Train:
The Gatwick Airport Train Station is located just outside the terminal. The Gatwick Express is the quickest options. This train departs every 15 minutes, takes about half hour and a one-way ticket is £ 20. Or you can take the Southern Railway which follows same route as the Gatwick Express but it stops at intermediate stations and takes 5 minutes more, one-way ticket is £ 14.40. The best rail option is the Thameslink which will take you to Kings Cross station in 45 minutes for just £ 10.
Bus:
EasyBus and National Express run shuttle bus services from the airport to London Victoria and Earl's Court. Departures are every half hour, one-way ticket £ 7 and the journey takes about 1,5 hours. There are also direct buses to London Heathrow and Stansted Airport.

Considering the long distance you need to travel to downtown London a taxi is not the best option. It can take 2 hours and costs £ 70 or more. Better take a train first and then switch to taxi.