Here are some of the different types of plane models you can buy.
Electric rc planes are quiet and easy for a beginner to maintain. Simply charge the battery pack and you can fly for 10 - 20 minutes per battery charge.
Gas rc planes are noisier and use special hobby quality nitro fuel. These models are faster and slightly more complicated. Suitable for intermediate to advanced modelers. They also tend to go a lot faster than electric models.
Airplane kits come unassembled, and in some cases you would need to buy the radio control system, the motor and other accessories separately. If you are a beginner, the ARF or RTF models are recommended.
ARF means almost ready to fly. These are usually kits that come with all accessories needed, but would require some assembly. It may take 1 hour or more to get the model plane from the box to flying in the air.
RTF means ready to fly. These are the most complete kits that require very minor assembly skills. Usually you can start flying 15 minutes from opening the box. All you would have to do is attach the wings, charge the battery pack and start flying.