What do the 'approved', 'pending' and 'cancelled' point statuses mean?

The statuses will change depending on your order status.

Approved: These points can be redeemed on rewards immediately
Pending: These points are need to be verified before you can redeem them. This typically applies to purchases and referrals
Cancelled: These points will not be added to your account. For example, this will happen if you cancel a purchase (the points will change from pending to cancelled)