Even if the extent of your home cooking is making out-of-the-box macaroni and cheese, a strainer is essential. Strainers are simply bowls with holes in them that allow liquids to drain out, leaving solid foods inside. They're indispensable for separating pasta from the water you just boiled it in, beans from the juices they're canned in and many other instances where you want to get rid of excess liquid. They're also a great place to rinse berries, veggies, beans and even lettuce.
Strainers come in many shapes, sizes and materials. They even have different sizes of holes. A colander, a type of strainer with relatively large holes, is usually used for larger foods like pasta and vegetables. The main drawback to colanders is that they only work for foods that are larger than the holes, so some people opt for fine mesh strainers that have smaller holes to separate finer ingredients.
You can use mesh strainers just like a colander to drain water or juices, but they also go a step further. Because the holes are very small you can use them to separate the fat out of gravy, seeds out of a raspberry puree, or chunks out of sauce. But that's not all -- you can even use them to sift flour or powdered sugar when a recipe calls for it. While a colander might adequately meet your everyday cooking needs, choosing a fine mesh strainer will give you the most versatility. Or since they're inexpensive, just buy one of each.