Merino wool is regular 100% wool, however it comes from a Merino sheep whose fleece is very fine and soft, hence the buttery softness of merino wool. If you want next to the skin softness, merino is the way to go.
Also, FYI... you can wash wool in cold, warm or even hot water. The temperature is not what felts wool, but rather agitation and rapid temperature changes. IE: If you wash in warm water, rinse in warm water as well. And always, be it cold, or hot water, never agitate your wool.
Wool can absorb up to 30% of it's own weight in water, and get this... still feel warm and dry. That is why wool is so perfect for fisherman sweaters. Those Irish are little McSmartypants.