echo

Display message on screen, writes each given STRING to standard output, with a space between each and a newline after the last one.

Syntax
     echo [options]... [String]...

Options

 -n
     Do not output the trailing newline.

 -E
     Disable the interpretation of the following backslash-escaped characters.

 -e
     Enable interpretation of the following backslash-escaped
     characters in each String:

    \a          alert (bell)

    \b          backspace

    \c          suppress trailing newline

    \e          escape 
 
    \f          form feed

    \n          new line

    \r          carriage return

    \t          horizontal tab

    \v          vertical tab

    \\          backslash

    \NNN
          the character whose ASCII code is NNN (octal); if NNN is not
          a valid octal number, it is printed literally.

    \xnnn
          the character whose ASCII code is the hexadecimal value 
          nnn (one to three digits)

This is a BASH shell builtin, to display your local syntax from the bash prompt type: help echo
There is also an echo utility (man echo) , but the shell built-in version will generally take precedence.

Examples

echo "Hello World"

DEMO=Testing123
echo "$DEMO"
# Testing123

echo "with quotes we can echo
several lines at a time"

Echo can also display in color by using Escape sequences for foreground (30..37) and background (40..47) colours.

$ COL_BLUE="\x1b[34;01m"
$ COL_RESET="\x1b[39;49;00m"
$ echo -e $COL_BLUE"Important Message: "$COL_RESET"This is a message"

Here is a shell script to display all the color combinations:

 #!/bin/bash
 #
 echo ---Bg---40---41---42---43---44---45---46---47
 for i in {30..37} # foreground
 do
 echo -n -e fg$i- 
 for j in {40..47} # background
 do
 echo -n -e '\E['$i';'$j'm SS64'
 tput sgr0 # Reset text attributes to normal without clear
 done
 echo # newline
 done
 
 echo -- Clear BG --
 for n in {30..37} # foreground
 do
 echo -e fg$n '\E['$n';'01'm SS64'
 tput sgr0 # Reset text attributes to normal without clear
 done

“The only thing that helps me pass the time away; is knowing I'll be back at Echo Beach some day” ~ Martha and the Muffins

Related linux commands:

head - Output the first part of file(s).
less - Display output one screen at a time.
more - Display output one screen at a time.
notify-send - Send desktop notifications.
pg - Display one page at a time.
tee - Redirect output to multiple files.
Equivalent Windows command: ECHO - Display message on screen.