Linux utility time is used to run programs and summarize system resources usage.
time runs the program COMMAND with any given arguments ARG… When COMMAND finishes, time displays information about resources used by COMMAND (on the standard error output, by default). If COMMAND exits with non-zero status, time displays a warning message and the exit status.
The following example shows how to check how much time it takes to copy 4 GB data from one USB disk to another:
time dd if=/dev/sda of=/dev/sdb
time can be used as a prefix for any Linux application you run to check how much time it takes to get this app. finished. Very useful one.