The Autotools are a group of programs that create a GNU Build System for a given software package. It is a suite of tools that work together to produce various build resources, such as a Makefile (to be used with GNU Make). Thus, Autotools can be considered a de facto build system generator.
Some notable Autotools programs include:
In general, Autotools is meant to generate the Unix-compatible script and Makefile to allow the following command to build (as well as install) most packages (in the simple case):
./configure && make && make install
As such, Autotools also has a relationship with certain package managers, especially those that are attached to operating systems that conform to the POSIX Standard(s).