chvt: change vitrual terminal.
Linux is a multiuser operating system so multiple users can work on it parallely by logging in using different terminals. This is generally achieved by using the cntrl+(left)alt+Fn key where Fn is the function keys from 1-6. Thus So there can be 6 users working on these six terminals at the same time but only one of them will have the GUI.
In case you want to change between these terminals from the command line then you can use the command chvt.
where n is the terminal number. For eg :
$ sudo chvt 1
is equivalent to cntrl+(left)alt+F1