For hand needles, the larger the number on the needle, the thinner the needle....For hand quilting, I use a number 9 or 10 between.
Sewing machine needles are different. The larger the number, the thicker the needle. And sewing machine needles have 2 numbers. 70/10 is a thin needle for delicate work. 90/14 is thicker and works well for denim, etc. The standard size is 80/12.
Thread numbers get larger the thinner the thread. Standard sewing thread is #50. Quilting thread is a little thicker (and I always try to get the waxed kind for strength) #40. When I machine quilt I make sure that the top thread and bobbin thread are the same. If they aren't most machines will revolt!! .... don't forget to check the tension when changing thread.
Hope this helps.