Creating an AWS Account
It is necessary to provide a payment method (Credit or Debit card) to use AWS, including the free tier. Be careful about this - many people have complained that they end up getting charged surprise fees even though they never intended to go over the data caps for the “free” services.
Creating a Sub-user
While it is possible to use your root AWS account for managing services, this is not recommended.
The principle of least access is that no account should have more privilege than is needed. This will limit potential fallout in the case that any of your account keys are breached.
Those familiar with UNIX systems understand that the root user is not meant to be used for normal operations, and in AWS it is recommended that you create a sub-user for managing AWS services.
This is kind of like having a luxury car that has a “valet key”, which is basically a key that can start the engine, but won’t allow the glove-box or trunk to be opened (to prevent theft).