build-essentials is an Ubuntu package which depends on a number of important libraries, gcc, the associated toolchain, etc. Just installing a pre-compiled packa

build-essentials is an Ubuntu package which depends on a number of important libraries, gcc, the associated toolchain, etc. Just installing a pre-compiled package won't require a compiler though, it's only when you want to build something from source that you need it. There are a number of python packages that don't come pre-compiled; that may be what you were seeing.