When you drive your car, the radio will impress information onto the carrier wave. The type of information that is impressed onto the carrier is: going left / right and how far to the left / right, go forward / backwards and how fast forward / backwards. Unfortunately, each of these functions is also referred to as a 'channel'. So a radio that can control steering and speed will be a 2-chanel radio. These channels are different than the channels for the carrier frequency; it is just a confusingly similar label. The receiver in the car then decodes this information, and generates appropriate electrical signals for the devices that are connected to it: the steering servo and the speed controller. These devices then transform those signals into the physical: your car moves! The term 'proportional radio', which might pop up while you're shopping, means that as you press more on the throttle the car moves proportionally faster; same goes for the steering. This is opposed to simple on-off control: the car is either standing still or going full blast - most toy R/C cars use on-off radio control. Check http://www.howstuffworks.com/rc-toy3.htm for a different explanation of the same thing, and with pictures. ;) All of this is quite simplified here. If you want more (technical) detail you can look up how a radio works in any electronics communications textbook. The method used to generate the radio signal (the modulation) is pretty standardized. The way to impress the information onto that carrier signal is different for each manufacturer. This means that radio made by company A will probably not work with a receiver made by company B, even if you have matching frequency crystals. The whole set: radio, receiver, and crystal set come as a matched set. There are third party manufacturers that make receivers that are compatible with first party manufacturers. Check with the manufacturer of your equipment before you commit to a purchase! One thing worthy of note is that crystals (channels) are interchangeable between AM and FM radios made by the same manufacturer. However, the radios are built so that crystals are not interchangeable between manufacturers - you need to buy crystals made for your brand of radio. There is also something called a 'synthesized frequency module'. This is referred to differently by different manufactures, for example: 'spectra module', 'synthesized transmitter', etc. The idea is rather simple (to the end-user anyway). There is an extra piece of electronic built into the radio that will allow you to dial in the desired frequency: no more crystals to swap. You can (but do not have to) get a receiver with the same thing in it. Another feature is something called Battery Elimination Circuit - BEC. Normally you need a battery pack connected to the speed controller which drives the motor, you also need a separate battery pack to power the receiver itself. Most receivers today have a BEC, which eliminates the need for the battery pack going to the receiver. The receiver gets its power from the motor battery pack. Less weight for your car to carry, less run time though; the tradeoff is worth it however.