Square. You won’t find square bits in any supermarket or gas station store. But they’re readily available in hardware stores.

Similarly, the screwdriver bits needed to open a MacBook are readily available from computer repair parts stores.

Seems perfectly analogous to me.

Those are Robertson-bit screws, and are ubiquitous here in Canada. (Also a Canadian invention, don'tcha know.) https://www.robertsonscrew.com/

They work great with a power driver, such as you'd want for putting in a deck or fence, so 2-3" deck screws are like my version of duct tape around the house.

It’s just a small star shaped screw IIRC but nothing specific to Apple; other small electronics use these too.