Most cars have at least one "dome light" (or "courtesy light") located in or near the ceiling of the passenger compartment, to provide illumination by which to fasten seatbelts and enter or exit the car. These often have an option to switch on when the front (or any) passenger doors are opened.
see courtesy lamp by http://www.linhongled.com/led-courtesy-lamp/
Many vehicles have expanded this feature, causing the overhead interior light to remain on after all doors are closed, allowing passengers to fasten seat belts with added illumination. The extended lighting cycle usually ends when the vehicle's ignition has begun, or a gradual reduction in light emitted after a couple of minutes if the car isn't started, called "theater" lighting. Interior lighting has been added on some vehicles at the bottom edge of the dashboard, which illuminates the floor for front passengers, or underneath the front seats at the rear, to illuminate the floor for rear seat passengers. This type of convenience lighting approach is also sometimes used to illuminate interior or exterior door handles, exterior step running boards, or electric window switches.
LED light sources appear increasingly as interior convenience lights in various locations, especially with finely focused lighting on console control surfaces and in cabin storage areas.
Map lights are aimed at specific passenger positions and allow for reading without glare distraction to the driver. Some vehicles have "approach lighting" (puddle lights) in the exterior mirrors or lower edges of the doors, as well as interior lighting activated via key fob. Many cars have lights in the trunk (or boot), the engine compartment, and the glovebox and other storage compartments. Modern pickup trucks usually have one or more white cargo lights which illuminate the bed of the truck, often controlled in conjunction with the interior dome lighting.
Most instruments and controls on a dashboard in modern vehicles are illuminated when the headlamps are turned on, and the intensity of light can be adjusted by the driver for comfort. Saab automobiles, for example, have an aircraft-style "night panel" function which shuts off all interior illumination save for the speedometer (unless attention is called to a critical situation on another gauge) to improve the driver's night vision.