Is "minetest" library, table or folder?

[Andrey01]

For example, when we are calling the function minetest.register_node(), what does "minetest" mean? I would assume this is a table, because there`s field "register_node" refers to the function where it is created in "minetest" table.

Although, for example math.abs() function looks like "math" is a library where abs() function is defined.

[rubenwardy]

Both math and minetest are tables, however the math table is defined by the math library