Execute Multiple BASH Shell Commands

How to run shell commands sequentially or at the same time entered on a single line.

echo 1
sleep 5s
echo 2

(A) run several commands using the control operator ";" (semicolon) which will execute them sequentially. The shell will wait for each command to terminate in turn. The return status is the exit status of the last command executed.

echo 1; sleep 5s; echo 2

(B) run several commands using the control operator "&" (ampersand)

echo 1 & sleep 5s & echo 2

(C) run several commands using double ampersands

echo 1 && sleep 5s && echo 2