Gatwick Airport enjoys links to many international airports and you can check on flight progress here.
There are two terminals at Gatwick the North Terminal & the South Terminal - the south has a train station. There's a little shuttle service (free) which runs between the two terminals & does the trip in a minute or two.
Leaving/Getting to Gatwick
If you're planning to fly into Gatwick, you can easily pick up a hire car but the airport also has a train station with links to London & Brighton, Horsham, Crawley, Croydon, Portsmouth (that's further afield in Hampshire), Billingshurst. The Gatwick Express leaves for London Victoria every 15 minutes. Check for engineering works before you travel, especially at weekends. Tickets bought for the Gatwick Express are not valid on other routes.
Parking at Gatwick Airport
Parking at Gatwick in the short-stay car parks seems to have rocketed in cost recently - a stay under 4 hours cost me £14... but other options are available...A2Z Airport Parking gives you the chance to search and compare the most suitable airport parking services.
Car Hire at Gatwick Airport
Car hire is very well appointed at Gatwick with all the major agents based on site, such as Avis, Hertz & Europcar. It's highly recommended to book in advance via an aggregator such as Rhino Car Hire.
Route planner (RAC)
National Rail timetables
There are a good number of them! The M23/A23 does the London-Brighton route, passing Gatwick Airport en route. It connects with the M25 which runs around London and is known to many locals as the Magic Roundabout after the children's programme).
The A272 passes in a west-east direction from East Sussex to Hampshire, taking in towns such as Haywards Heath, Billingshurst, Petworth, Midhurst, and smaller villages like Coolham and Cowfold.
The A27 also runs in a west-east direction (or vice versa) but it's on the coast, so it picks up Brighton, Arundel, Chichester and then on to Hampshire. And there are tons of other roads as well, some tiny but offering routes into villages, hamlets & small towns.