gas lift is an oil production technology where gas is injected into the well fluid "down hole". The purpose of this is to lower the density of the liquid collumn in the well so that the liquid can flow more easily. The gas is usually transported down in the annulus between the casings that makes up the well. (im actually not a petroleum/drilling person so some of the terms may be wrong but the pricple is ok).
Its not related to centrifugal pumps in any way.