Explain 'cd' command usage.

The cd command is used to change the current directory in the terminal. Here’s how to use it:

cd [directory]

Change to a specific directory:
```
cd /path/to/directory
```
This command changes the current directory to the specified path.
Change to the home directory:
```
cd ~
```
This command takes you to your home directory.
Change to the parent directory:
```
cd ..
```
This command moves you up one level in the directory hierarchy.
Change to the previous directory:
```
cd -
```
This command switches back to the last directory you were in.

To change to a directory named "Documents" located in your home directory:

cd ~/Documents

Using the cd command effectively allows you to navigate through the file system in the terminal.