Crewels needles have an larger eye on these needles, so it lets them carry a heavier weight or more thicker thread yarn than other needles. With the sharp tip it can easily go through and pass through loosely woven fabric such as Adia which is an even weave fabric without catching or tearing it. Golden eye refer to the coating of the inner needle, which allows the ease of the threading of the needle.
Crewel technique is not a traditional embroidery but is a style of free embroidery.
They are like a sharp needles but generally have a larger eye in all sizes.