I've been using the Casio PT-100 for about ten years and it was one of the first keyboards that I ever used. Because of its extremely small size and mini keys, it is great for kids to play and learn on. While it is somewhat limited in its variety of sounds and features, it has enough things on it to suffice for this type of keyboard. It contains a switches for choosing your sounds, as well as buttons for different demo songs and rhythmic patterns. There are also sliders for volume control and a few other things. It has built in speakers and it is powered by power supply that comes with it, although I'm not sure how much voltage is required. For the first octave to the left above the keys it shows what each note is, which is definitely a good feature for kids looking to learn the keyboard. By modern standards, this keyboard seems primitive but for the time this was a great little keyboard for messing around with. Obviously one of the best parts about the Casio PT-100 is how cheap the price is, especially now if you can find one used. Don't get me wrong, this isn't an outstanding keyboard by any means, as it is really more of a toy than an instrument. This being said, for kids and beginners looking to get a cheap, incredibly small and portable keyboard the Casio PT-100 is a nice choice. Casio is known for making cheap keyboards that are best suited for practicing and not for recording or shows, as the sounds just aren't too professional sounding or realistic. The sounds are certainly cheesy and sound like the time period that it can from but if you ever come across one of these little guys pick it up and try it out!