cd command is used to changing a directory,you can change the current directory to another directory in linux using this command.
it will change the current directory to demodir1
In linux,directory path are specified using the forward slash ("/") the double dots (..) pseudonym for the parent directory,which moves you to one directory level up.You can move up multiple level in the directory tree by specifying multiple ".." in the path(for example cd ../.. moves you up two levels. similarly dot(.) is the pseudonym for the current directory.