Half life or Steam?

hi i dont know what i really need to use esf do i need half life or could i use steam if i need halflife, which version?

Steam will fix itself automatically to the highest version. You'll need the Steam Pack, availiable at ESFstuff, to install it right.

For HL, you need version 1.1.0.9 minimally, but most servers are running 1.1.1.0. I suggest 1.1.1.0.