A UNIX command to force the root directory to become something other than its default for the duration of the current process. This may only be executed by privileged users to provide a process (usually FTP or HTTP) with access to a restricted section of the file system. The new root accommodates copies of all the required files and directories. See also FTP and HTTP.
A Unix system call that sets the root directory for a process to any arbitrary directory. The idea is compartmentalization: even if a process is compromised, it shouldn't be able to see interesting parts of the filesystem beyond its own little world. There are some instances where chroot "jails" can be circumvented, and it can be difficult to build proper operating environments to make chroot work well.
An additional root directory you can create to limit the server to specific directories. You'd use this feature to safeguard an unprotected server.
"chroot-ed" is the usual term in the Unix world to say that users are kept in a confined part of the directory tree. Trying to change to a directory outside of this limited area will fail.
A chroot on Unix operating systems is an operation that changes the root directory. It affects only the current process and its children. "chroot" itself can refer to the chroot(2) system call or the chroot(8) wrapper program.
