The //**echo**// command in Linux and Unix-like systems is used to display a line of text or a variable's value on the screen or in a file.

Here are a few examples of how the **echo** command can be used:

1. Display a line of text on the screen: <code>echo Hello, World!</code>

2. Display the value of a variable: <code>echo $HOME</code>
This will display the value of the HOME environment variable)

2. Write text to a file: <code>echo Hello, World! > testworld.txt</code>
The above will create a file named "**testworld.txt**" and write the text "//**Hello, World!**//" to it)

3. Append text to a file: <code>echo How are you? >> testworld.txt</code>
The above will add the text "//How are you?//" to the end of the file "testworld.txt". It's also possible to use the echo command to create a new line, by using echo -e with an escape sequence \n

For example:
<code>echo -e "Hello\nWorld"</code>
this will print "**//Hello//**" in a new line and "**//World//**" in next line

**echo** command is widely used in shell scripting and command line scripting, it's one of the most basic command and considered as one of the building blocks for more complex commands.