What does 3-6-1 Butterfly look like and what is it good for?

[Duncton]

Whenever I saw butterfly, I thought 3dc-2dml/r-2mc-2aml/r-1st.

I'm pretty sure this one is meant in counter formation table. I do like it, but I don't use it a lot since I don't often have both DML and DMR.

It should be most effective against formations without wingers and no more than two strikers (4-4-2, 3-5-2 flat). To use it against 3N-4-3, you'd have to be pretty sure of your defense.