With a regular subscription you can share your account with a friend or family member, but need to take into account that, if only one device is allowed, you both cannot connect in parallel. This means that if a friend of yours is surfing the Internet anonymously, using your account, you must wait until he disconnects before you can, in turn, connect using that same account.
This doesn't necessarely apply, if you are allowed to use up to three or five devices at the same time with one account (depends on your subscription). If you don't exceed your limitation of devices, you both can surf simultaneously on multiple computers or mobile devices, regardless, who owns the respective device.
Important: Please remember that you are solely responsible for your account. If you forward your login data to third persons you are also responsible to any actions taking place by others on that very same account.