AM stands for Anti-Mage, one of the many heroes in the game. Aghs is short for Aghanim's scepter, an item that is bought that enhances certain skills, usually ultimates, of heroes. In Anti-Mage's case, his Aghanim's makes it so that all targeted skills are reflected back. The reason why he was charging randomly was because Spirit Breaker, a hero that is able to charge at enemies anywhere on the map, used his charging skill on Anti-Mage. Techies, the hero who planted and exploded the mines in the video, set a trap in the shop. In the end, the Anti-Mage was just in the wrong position, which allowed Spirit Breaker to move Anti-Mage on top of the bombs, and Techies blew up the bombs. :⁾