The term thread count is a measurement of the number of vertical and horizontal threads in a square inch of fabric. Many high end sheets boast thread counts of 600 to 1500 and the cheap scratchy sheets from your college days were probably around 100. The idea behind thread count is that the higher the thread count, the softer the sheets as the threads have to be finer in order fit them all in a single square inch. Finer threads result in a much smoother and softer fabric. However,thread count should not be the only factor when you purchase sheets. There are 3 more factors to consider.
Ply: This is the number of threads twisted around each other to make one single thread. Two threads=2-Ply, 3 threads=3-Ply. You get the idea. Some manufacturers use 2-ply threads allowing them to count both threads thereby giving them a higher thread count but not in the way you thought! Single ply, which is a single thread, is the preference when counting threads!
Yarn Size: Fine thin cotton threads make for a soft and smooth fabric because more threads can fit into the square inch. Finer threads also mean that the threads are more delicate and so proper care should be taken in caring for your fine sheets.
Material Quality: Egyptian cotton and Pima cotton are two superior types of material used to make sheets. Polyester can also be blended with the cotton to reduce wrinkling, which is also important factor to consider.
When choosing sheets you should look for a thread count above 300with single ply. Whether you prefer a polyester/cotton blend or a sateen or percale weave, it is entirely your decision. YOU have to sleep on the sheets so please choose what is comfortable for you.