Snowblades? What and who are they for??

[Mo2]

Have been out of the 'ski circuit' for te last 5-6 years (while having kids) and now everyone seems to be going on about snowblades for kids.
EBay has lots for sale which makes me wonder if they are actually one of those things which are nice in theory, but not really in practice?

Can anyone enlighten me?
Are they for adults or kids?
Beginners or competent skiers?
Do you use them like skates (no poles?) or what?
Are they for downhill, or for around the resort?

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To answer briefly !

Adults and older kids
Competent/good
No poles
Downhill

Apparently the fun is that they are easy to turn and go fast. Have heard they can cause more injuries though. Not something that appeals to me.