What's the meaning of the operator || in linux shell?

Question

I found this piece of code in a .sh script:

 (test -x "$1" || which "$1") 

What does this operator || mean?

Answer 1

it means:

if the first command succeed the second will never be executed

Answer 2

It's equivalent to boolean "or" with short-circuiting evaluation, such that it will execute the second command only if the first returns some value corresponding to "false". For example:

false || echo "foo"

echoes "foo", while

true || echo "foo"

Prints nothing. The && operator provides a complimentary operation.