Since more people are using Netflix over the years, it's only natural that they would want to share the wealth with their family and friends.
It's not possible to buy an actual subscription for others, but if you have an Amazon account, you can buy gift cards online, which can be used as prepaid Netflix gift subscription.
In order to redeem your gift card, you'll need to have a Netflix account. You can use your gift card to setup an account without using a credit card. Your subscription fees will be deducted from your gift card balance.