There are two types of asuras.
One type in the apayas: one of the four lowest realms. They are born there due cultivation of bad sankhara because of aimless, lazy gati (depended on others). These asuras are said live in the oceans and mountains on Earth (around us). They are called Vinipatha Asuras.
The other type are actually “asura devas” who live in the Chathurmaharajika deva realm. They are said to constantly fight with Tavatimsa devas headed by Sakka.
Also see, “31 Realms of Existence“.
P.S. I just revised “Asuras” to “Vinipatha Asuras” in the post, “Sīla, Samādhi, Pannā to Pannā, sīla, Samādhi“.