Chroot provides a way to setup an isolated environment inside an OS, where specific applications can run without interacting with the rest of the system. It is also called a jail and is often used to create a test environment for applications which may not be directly installed on the system due to various concerns like stability or security.
Running 32 bit applications in a chroot environment 64 bit ubuntu
Because chroot isolates application into a separate environment, it is also used to run 32 bit applications inside a 64bit OS environment. Now a days most OSes and applications are 64bit on both desktop and servers.