Electronics vs. Electrical DevicesBefore packing, understand the difference between electronics (computer, digital camera charger, DVD player) and electrical devices (hair dryer, electric shaver). Your electronics will likely work with the use of an adapter. To make sure, check the AC power adapter (that big black box that goes between your computer, for example, and the plug in the wall). On the back you'll see some information. Look for "Input". If it says ~100V-240V, you're fine to travel with it all over the world. All you'll need is a wall plug adapter (more about those below). If you're still not sure, you should check online with the manufacturer.
Your electrical devices are a different story. Your hair dryer, curling iron or electric shaver will require a converter if you're coming from a country that uses 110V (North America, Japan). A converter is a very large implement that converts the input from 220V to 110V for your device. If you don't use a converter, at best, you'll ruin your device. At worst, you'll see fireworks coming out of the wall socket.
My advice is to leave anything that requires a converter at home. Some larger, fancier hotels offer a 110V plug in the bathroom but it usually comes with the warning "for electric shavers only" (does anyone still use those?). Nearly all hotels provide hair dryers these days and if you absolutely need other things, like hair curlers, then look for a travel set that doesn't require a converter.
The Accepting Wall Sockets in ChinaNow to the actual wall sockets. See the photo at the top right. This is what most wall sockets look like these days in China. The top socket takes a two-prong plug. The prongs must be the same size ("Type A"), although many modern devices with Type A plugs have one wider prong. This type won't fit into a Chinese wall socket and will require an adapter. This socket will also take a "Type C" or "Type F" plug that is standard in Germany. (If you're coming from Europe, all your devices will work - China uses the same voltage.)
The bottom socket in the photo takes "Type I" plugs common in Australia and New Zealand. (All your devices will work if you're coming from Australia/NZ as well as you use the same voltage as China.)