One of the most common FC firmwares. Open source, available on GitHub. Very expandable, with fairly simple setup (Joshua Bardwell has great tutorials on it). Default tune is well-rounded for 5", and has sliders for very easy tuning.
Directly controls the speeds of your motors. Receives a signal from the FC and converts it into pulses to spin the motors. Comes in individual sticks or 4-in-1 stack-mount modules. 4-in-1 ESCs usually replace PDBs in a build. Can take a variety of input protocols, such as Dshot. Often has a telemetry and/or current sensing output so you can see the amp draw of your motors.
A fairly common flight control software, created by FlightOne. Focused on fast, simple setup with clean flight characteristics. Ships with different tune and rate presets. All configuration can be done via OSD. More limited than Betaflight in terms of peripheral support, and usually more expensive, but still a great firmware option.
First Person View is a mode of flight in which the pilot looks through a camera on the aircraft. This is usually achieved using a camera wired to a VTX and a pair of goggles with a video receiver. This is the flight mode most commonly used for racing, freestyle, and cinematic acro quadcopter flights.
Essentially the "brain" of your quad. Runs firmware such as Betaflight or FalcoX to take the input from your receiver (and any other peripherals) and sends the ESC a signal (usually Dshot) to spin the motors. Has a gyro to hold the quad stable and voltage regulators to power peripherals. Contains rate and PID settings to dial in the flight feeling to the pilot's preference.
FC firmware focused on being premium yet simple. Good flight handling, but possibly more limited than other options. Very few stack options, and usually very expensive, but the ones you can get are premium quality.
The mode of flight in which the aircraft is flown in third person. Tends to be slightly more difficult than FPV as it's a bit harder to keep track of the orientation of the quad. Can also refer to having the quad in a position in which you can see it.
The receiver wirelessly gets the signal from your radio and gives it to the Flight Controller. Usually outputs a serial signal and is often powered from 5v.
Takes the video from your camera or OSD and transmits it on a channel. Can be thought of in a similar fashion to analog TV; only one thing can be transmitted on a given channel, but everyone can watch it. Can either be analog or digital.