Android is Unix running on the Linux kernel.
The difference from Linux is it can’t be run as root.
This is to prevent users from trashing their system or unintentionally compromising it with malware.
On the whole, Unix OSes are safer than Windows.
From a *technical* point of view, it's not. Both Android and Linux (two separate products) are POSIX-compliant, which makes them look and act very similar to Unix, but the kernels are different enough that they are not considered to BE Unix.
From a user point of view, though, there is not enough difference to worry about.
If I am not mistaken Macs also run Unix.