Sharps are the needles most commonly used for hand sewing. They do have a sharp point, as the name implies, and are of medium length (compared, that is, to the short quilting needle or the long milliner's needle, below). Sharps have a rounded eye, which is usually just large enough to accommodate thread. Like the other hand-sewing needles, sharps are available in sizes 1 through 10, which is determined by the diameter of the needle. Size 1 is the longest and thickest, and size 10 is smallest and thinnest.
When choosing a needle size, it's best to consider the type of fabric you'll be using. In general, the lighter your fabric, the thinner the needle you'll want to use with it. Many craft stores stock packs of assorted sizes. If you're unsure of the best needle, just try passing a few different-sized needles through an inconspicuous place on the fabric. Which one passes through most easily? Which one leaves the smallest hole in the fabric?
Ball-point needles have a rounded tip, so they're perfect for sewing on knit fabrics. A sharp needle can easily damage knit fabric by poking though a thread and then pulling out the knit stitches. A ball point, on the other hand, will pass right through the knit. Ball points also come in sizes 5 through 10.
Embroidery needles (sometimes known as crewel needles) are very similar to sharps. The main difference is in the eye—embroidery needles have a larger eye, so that thicker flosses and yarns can pass through. Embroidery needles also come in sizes 1 through 10.
Quilting needles, which are also known as betweens, are much shorter than sharps and also have a small, rounded eye for thread. This type of needle is a bit thinner than a sharp as well. Quilting needles are great for small, detailed stitching, such as quilting, of course. Their thinness and small eye help them pass easily through heavyweight fabrics, like denim or tweed. This type of needle is available in sizes 1 through 10.
Milliner's needles are the longest of the hand-sewing needles. They are traditionally used for hat making but are also great for basting, as you can manoeuvre them quickly through fabric. They're also available in sizes 1 through 10.
Now, there are also "specialty needles," which are used for other purposes. Here are two that are commonly used by crafters:
Tapestry needles have a blunt point and a big eye. They're made this way so they can pass through needlepoint and tapestry canvases without damaging them. And that large eye will accommodate the thicker yarns used for these kinds of crafts.
Chenille needles also have a large eye like tapestry needles, but they have a sharp point. This makes them ideal for crafts like ribbon embroidery, where you need to pull a thick strand through a closely woven fabric.