Based on limited research that I’ve done recently, it seems that the triangle formation is an attacking formation used primarily by midfielders to advance the ball by forming a rotating triangle pattern on the field and exploiting the many passing lanes that it can create in the defense. Is this understanding correct?
Chelsea under Mourinho used a defensive triangle anchored by Claude Makelele, the advantages of which are described here by the coach himself.
Look, if I have a triangle in midfield – Claude Makelele behind and two others just in front – I will always have an advantage against a pure 4-4-2 where the central midfielders are side by side. That’s because I will always have an extra man. It starts with Makelele, who is between the lines. If nobody comes to him he can see the whole pitch and has time. If he gets closed down it means one of the two other central midfielders is open. If they are closed down and the other team’s wingers come inside to help, it means there is space now for us on the flank, either for our own wingers or for our full-backs. There is nothing a pure 4-4-2 can do to stop things.