I grew up around this hobby, my Dad built and sold them back then. Me and him fly them when we get the chance. His airplanes will be pictured here as well as mine. Together we have more than 35 years of tinker time with this hobby.
Its both a relaxing and exciting hobby.
I must also warn you its addictive and don't worry we all crash our aircraft, but if you start out with the right trainer and simulator you will repair and fly again.
First a crash course in what the types of aircraft have in common.
Step 1: Common to all types of RC airplanes-Radio
The radio transmitter and receiver: This is your link to the aircraft never scrimp when it comes to the radio, if it glitches you can crash or worse hurt someone. Radios come with two or more channels, the channels are also not what you think, they are not separate frequencies, instead they are each control. Most airplanes have 4 channels, rudder, ailerons, throttle and elevator. Sailplanes have just two or three. Radio transmitters are also on several radio frequencies and are set by the user by changing the matching crystals in the transmitter and receiver. Unless you have a newer radio that uses ultra high frequencies in the 2.4 gigahertz range, these radio's do not require crystals.
The radio receiver on gas powered aircraft is powered by a rechargeable battery, on an electric it can be powered by the same battery that powers the propeller threw a battery eliminator circuit.
The power is usually 4.6 to 6volts.
I have used several brands, most were good, as long as its a name brand one like Futaba, Airtronics, HiTec, or Tower hobbies (made by Futaba).
Its also a good idea if you plan on having more than one airplane you can get an extra receiver on the same frequency and use one radio with several airplanes. This is what I do, I have a programmable radio with six memories so I can switch between them. I simply bought a receiver for each airplane, much cheaper than another radio.