Payment information

The one-year free usage limit after the AWS account is created is listed in the following document.
Fees will be charged for creating resources outside of the free usage quota.
Therefore, you need to register your credit card and other payment information.
https://aws.amazon.com/free/?nc1=h_ls&all-free-tier.sort-by=item.additionalFields.SortRank&all-free-tier.sort-order=asc&awsf.Free%20Tier%20Types=*all&awsf.Free%20Tier%20Categories=*all

Free tier lasts for 12 months, but it doesn't mean that everything is free for 12 months. On the other hand, some things will continue to have no charge even after that time.

Some things are free (within certain limits) for 12 months e.g. EC2, RDS, S3; some are free (with limitations) for shorter - e.g. Lightsail (3 months), Redshift (2 months), Macie (30 days). See https://aws.amazon.com/free/

Payemnt info is needed in case you go over these free tier limits, or if you provision resource(s) that sit outside free tier. But it's usually quite easy to stay within the free tier limits. Just be conservative when creating things and remember to clear things down when you're finished with them. You could also setup a CloudWatch alarm (you get 10 of them for free within free tier) to warn you if it looks like you're starting to accrue charges https://aws.amazon.com/cloudwatch/pricing/?loc=ft#Free_tier

To see what you have running and could potentially incur a charge after free tier ends, go to AWS Console, click on your name on the top right and select Billing Dashboard. Look at previous bills (I guess these will all be $0.00 but it might give you an idea of what would have been chargeable) by selectong Bills from the left-hand pane and then scrolling down to Charges by Service (this also breaks things down by region, which is handy for spotting things in a region you forgot you used to do something in).

You can also take a look at AWS Cost Explorer https://aws.amazon.com/aws-cost-management/aws-cost-explorer/