What do $? $0 $1 $2 mean in shell script? [duplicate]

These are positional arguments of the script.

Executing

./script.sh Hello World

Will make

$0 = ./script.sh
$1 = Hello
$2 = World

Note

If you execute ./script.sh, $0 will give output ./script.sh but if you execute it with bash script.sh it will give output script.sh.