If the statement would be correct without continuation, you need to use . Therefore, the following works without a backslash, as you can't end a command with a &&:
echo 1 &&
echo 2
Here, you need the backslash:
echo 1 2 3
4
or
echo 1
&& echo 2
Otherwise, bash would execute the command right after processing the first line without waiting for the next one.
# --------------------------------------------------------------------------------- #
# Para utilizar saltos de linea en la orden echo utilizar la opción "-e" y #
# todo el texto entre comillas dobles. El salto de linea se representa como "
" #
# --------------------------------------------------------------------------------- #
# To use line breaks in the echo command use the "-e" option and #
# enclose all text in double quotes. The line break is represented as "-e". #
# --------------------------------------------------------------------------------- #
##################################### EXAMPLE #######################################
echo -e "
testing line breaks with
the echo command
"
########### OUTPUT #########
| --------------------------------- |
| |
| testing line breaks with |
| the echo command |
| |
| --------------------------------- |