Cement is the dry, powdery substance that binds all masonry projects together. If you mix it with water and sand, you get mortar. When cement is mixed with water, sand, and gravel, it becomes concrete. Unless you're planning to build a large wall, buy your mortar already mixed. Just scoop it out and trowel it on. For concrete, the simplest solution for most household jobs is to buy it with the cement, sand, and gravel premixed in a bag. You just add water and stir it together. A 60-pound bag will make about half a cubic foot of concrete. If you choose to make your own, the normal recipe is three parts of gravel, to two parts sand, to one part cement. Add enough water to make a thick, mud-like mixture. Test the sand first. If it's wet, you need to decrease the amount of water you'll use. Add the water slowly. The idea is to coat each rock and grain of sand with cement. To test when it's done, make a pile and flatten it by smacking it with the back of a shovel. Use the tip or side of the shovel to make a series of ridges. These will be distinct in a good mix. If they're ragged, the concrete is too dry. If they fill in, it's too wet. Small batches can be made in a wheelbarrow or any large container that can be rinsed out afterwards. For larger jobs, you'll save hours of hard work by renting a power mixer. For anything requiring more than a cubic yard of concrete, it's best to call a ready-mix company and have them send a truck over.