When I got my first sewing machine in 1954 there was only one kind of needles, sharps. By the 1970's when polyester doubleknit was the fabric of choice for clothing, the ball point needle was invented. A sharp needle on the doubleknits just bounced and couldn't penetrate the fibers so you got skipped stitches. The ball point needle actually went between the fibers and produced a perfect stitch.
Then they invented the universal needle. It is halfway between a sharp and a ballpoint. It is called universal because it works on most fabrics. It has a slightly rounded point. This solved the problem for people that didn't know what type of needle they needed. However when you get into tough fabrics like denim, you need a sharp needle but not necessarily a bigger needle.
I worked off and on at a sewing machine store for over 30 years. The majority of the people who came in didn't have a clue what type of needle they needed, they just wanted a larger one. Then they were getting a lot of puckering with the larger needles because they punch bigger holes in the fabric. In most cases with heavier fabrics, you need a sharp needle but could still use a sz. 80. So then denim needles were introduced. Rather than telling you it is a sharp needle, they named a type of fabric that it could be used successfully on.
Then the needle companies decided an even broader range was necessary. Now you have to know both the type of needle and the size of the needle when you go to a store to purchase them. Not all sales people are created equal. I have met employees of fabric stores that have never changed a needle and can't help you with your choice. I was one of the other kind. I probably gave the customer too much information about the needles.
One needle that seems to be a problem solver for a lot of people is the topstitching needle. It is a sharp and has a larger eye so the stitch connects better through thick fabrics. Topstitiching needles are also needed when you use heavy weight thread. Now there are quilting needles which also make the stitch connect better in thickness.
Microtex needles are sharps and are the most tapered. They were made for microfibers like your silky shirts. They are also great for piecing on quilting weight fabrics. I use size 70 for piecing regardless of which style needle I am using. This creates less puckering of seams.
So now on to sizes, 60 is very fine, 70 lightweight, 80 midweight, 90 and larger, heavy duty. For piecing 70-80 is sufficient, for quilting 80-90. For sewing heavy canvas you might like a sz. 100 but make sure that is a sharp, not a universal. Remember sharper, not larger works in most cases.
If you have a Singer machine with a drop in bobbin, Singer brand needles might be your only choices. Other needles may cause skipped stitches. You should never use Singer brand needles in any other machine because it could damage the hook area of your machine. Unfortunately Singer does not make as large a variety of needles to choose from.
Is that more than you ever wanted to know about needles?