First of all, searing is not simply for steaks. The secret to a great prime rib is to start it at a high temperature to sear the surface and then lower the temperature to finish it off. Pork chops, chicken, and roasts all benefit from searing, though maybe not the way you think.
Browning, also known as the Maillard reaction or caramelization, is caused when you heat sugars and amino acids together. This reaction occurs in meats heated to temperatures between 300 and 500 degrees F. This reaction is what causes that very flavorful and wonderful crusty surface in meat that gives it that great, grilled flavor. Without this browning a steak just isn't right. So to get a great browned piece of meat you need to cook it at temperatures above 300 degrees F.
Charring is when the surface of meat breaks down completely leaving you only carbon. This typically happens on a grill where the meat meets the metal. Charring is bad. Not only doesn't it taste good, but charred meat is very bad for you. The breakdown of complex molecules in meat creates cancer causing substances. Charring can occur when meat comes in contact with something more than 500 degrees F. or if you overcook it. Of course a certain amount of charring is inevitable, after all you are putting raw meat in contact with very hot metal.
So what is searing? By definition, searing is to cook something hot and fast to brown the surface and to seal in the juices. Yet many of the leading cooking experts agree that searing does not seal in juices. Harold McGee in his book On Food and Cooking shows scientifically that a "seared" steak has less juices than an equally cooked not "seared" steak. Frankly the idea that you can somehow melt the surface of the meat into a material that holds in all the juices has always seemed a little strange to me. Conclusively it seems that science is agreed that sealing in juices just doesn't work and is not the real goal of searing. Searing is a process of cooking that creates the crusty surface texture most people find appealing and the caramelized sugars that gives us that steak flavor we want.
Some will say that you need something like a blast furnace to get a great sear. Makers of infrared grills are always talking about temperatures over 700 degrees to get a good sear. Of course they also say that you can only use this kind of heat for about 60 seconds before the surface of the meat begins to burn and char. What we want is a juicy piece of meat so the first rule has to be not to overcook it. Since there is no magical sear that will hold in the juices especially on a steak grilled to well, you need to get that steak off the grill at the magic moment and not a second later. Another thing to know is that most any grill that is working correctly can sear meat, you just have to do it right.
So how do you get the right sear? The first rule of searing is not to be timid. Just because that pork chop has started to brown doesn't mean that it's time to flip. Look for a dark brown color before you flip and not just a nice golden color. Dark brown, but not black either. This browning is what's going to give that steak the flavor and texture you want. If you sear for the flavor and not the juices and don't over cook, you will get a great piece of grilled meat.
The process to a good sear needs to start before you light the fire. You must have a good clean cooking surface. This will allow for even contact between the meat and the metal. You can oil the cooking grate, though with fattier meats you won't need to, but if you do oil the grate you need the right oil with a high smoke point. Safflower, canola and sunflower oils break down at much higher temperatures than oils like olive or lard. Once the oil breaks down it produces smoke and a bad flavor. So if you're oiling the grate use one of these oils.
For the meat you need to make sure that it is dry on the surface. Marinades are okay as long as you let the marinade drip off the meat first. Water is particularly bad because its going to turn to steam almost instantly and will actually lift the meat from the grate until that steam can escape. This will create uneven grill marks and also cool of the grate reducing the sear. Meat that is dry on the surface is best, but of course we all know the benefits of marinades when it comes to the bad things that can form on grilled meats.