A ring sling is made by stitching a long piece of fabric (approximately 2m) over two rings, you then thread the fabric through the rings to create your pouch. The rings mean that unlike most pouches you can easily adjust the size of the sling.
Ring slings are suitable from birth right through to preschool. Isaac's first sling experience was in a ring sing and if it had not been for his middle of the night appearance he would have gone in a sling sooner. It is a common misconception that babies must be worn 'legs in' when newborn but this is not the case. You may, if you so wish, have baby legs out from birth. The key is to not over spread their legs, rather ensure there is 1/3 of the material under baby's bottom to create a secure seat.
There are several styles of shoulder on ring slings and this can be as confusing as using the sling itself. Not every style of shoulder will suit everyone or you may simply prefer one over another. When discussing 'the shoulder' we are referring to how the fabric has been positioned before the rings are sewed into place. It then effects how the slings sitson your shoulder. There are four main types of shoulder - gathered, pleated, hotdog and box (Oscha). This blog by Sheffield slings explains the different styles in detail. I personally love a gathered shoulder for the way it spreads widely over my back up and I like the box pleat of my Natural Mamas Oscha as it is very supportive. But it is personal preference so make sure you try the different types before deciding on your favourite.
Padding. What is it and is it necessary? To answer the second question first, no it isn't necessary. But some slings (eg Ellaroo, Maya, Palm and Pond) do have padded rails. This provides cushioning for baby's legs but it can make slings difficut to adjust, especially if you are smaller and need to make sling smaller than where the padding has been positioned.
Ring slings are beautiful, stylish and practical. If you want to try one then have a go. There are lots of videos on YouTube. This one shows how to use a ring sling (legs out with a newborn).