You can feel the spiritual power of this Sufis dancing in this video. You can feel the energy that emanates from their chanting, their circling, the clapping and pounding.
This kind of ritual is rare in the Muslim world, but still exist in some part of the world.
They are Chechen Sufis as part of a larger group of Sufi brotherhoods. Chechnya is mostly Muslim, and they relate to the Shafi'i school of thought. Their mystical tradition is mixed of muridism (according to Arabic Al-Ma'ani dictionary, murid means adherent or disciple) and in which a Murshid (spiritual teacher or guide) plays a central role in the spiritual journey. Some of Chechen associate themselves with different branches of Sufism. Mainly there are two tariqas (order) in the north of Caucasus region: Naqshbandiyah and the Qadiriyah.
The word that they keep repeating is 'Yahu or Yahoo,' not the website though, it is an Arabic term and is a pronoun for God. In Hebrew language, it means God. You also here the chant, "La ilaha illallah," which means there no deity but God.
I shared this video with someone who asked me, "where are the women?"
I wrote back and said: That is a question that can't not be answered so easily. There have been women Sufis but not many, and they were mostly secluded from public gathering like the ones you saw in the video. The reason is very obvious. From religious and Sufi point of view anything that is considered distracting, or source of temptation must be avoided. This is a backward belief which dates back to maybe one thousand years ago, but there are some changes made in recent decades. Let's hope that one day Sufis wouldn't think women as threat to their purifying spiritual endeavor, rather see them naturally a graceful and blissful companions.