There are TWO versions to this tactic. An explanation of how and when to use the tactics is in the video.
Atlético Madrid set up in a 3-5-2 formation, with their width provided by their wing-backs and their wide-centre backs occasionally overlapping, more so on the left side. The right-sided central midfielder is responsible for breaking forward and attacking the right half-space, whilst the central and left-sided midfielder can be seen forming somewhat of a double-pivot. The two forwards look to occupy central defenders by Joao Felix playing a similar role as to a False 9, dropping deep and operating in the space created by his strike partner who pins and pushes back defences creating depth.
Out of possession, the 3-5-2 transitions into a 5-3-2 and Simeone has his side generally defending in a mid-block but against the bigger sides so to speak, Atleti defend in a mid-low block. They look to keep their midfield and forwards narrow, protecting the central areas and forcing teams out wide away from the goal. When defending the flanks, the team shift over remaining compact and narrow making sure to protect the channels.
In possession, no team in La Liga have scored more counter-attacking goals than Atleti. They've scored 6 on the counter and also strong from set-pieces scoring 8. Atlético are excellent in their transitions. Forcing the opponents out wide and regaining possession wide means Atleti have immediate forward passing options. As mentioned earlier, Atleti's left-CB operates as a wide-central defender and this allows the LWB to push higher as a winger.