Everyone needs bed linens, but often, people don't know much about how to purchase them. What is "TC" anyway, and why does it matter? What is the difference between a flat and a fitted sheet? What are "deep pockets?" Here are some answers about bed linens and buying them.

A typical sheet set, first of all, comes with a flat sheet, a fitted sheet and two standard pillowcases. The fitted sheet is elasticized all the way around the hem, with darts taken in at the corners to ensure a smooth fit over the mattress. The term "deep pockets" refers to fitted sheets that have more material to fit over the corners of the mattress. Mattresses are thicker than they used to be, and with the addition of features like the pillowtop, the fitted sheet needs to accommodate the corners without riding up.

A flat sheet is just that: a sheet that is hemmed all around and meant to be tucked in at the foot of the bed, over the fitted sheet. "Standard" pillowcases will fit over most pillows.

When buying bed linens, the shopper needs to consider size. Most people have queen or king-size beds, and the shopper should look carefully on the package for the size of the bed linens. King-size sheet sets may also have king-size pillowcases. These fit pillows that are longer than standard pillows. Most bed linens will also have the measurements of the beds they fit on the package, so a buyer can come armed with the length and width measurements of his or her bed and should be able to find appropriate bed linens.

Thread count is another aspect to consider when buying bed linens. Thread count refers to the quality of the sheet material. The thread count of a sheet is the number of warp and woof threads in one square inch of the fabric.

The lower the thread count, the thinner and lower-quality the material. Most people will want to look for a thread count of at least 250. Some bargain shopping Web sites also have sheets with much higher thread counts at great discounts, and these are great places to look for quality bed linens.

An average, 200-thread-count sheet set will run about US$25-$30, and the price goes up rapidly as the thread count increases. Higher thread count sheets are softer, thicker and more durable. They will last much longer and will "sleep" better, so a shopper should buy the best bed linens he or she can afford.