A service fro AWS which lets you easily provision, manage, and deploy public and private SSL/TLS certificates to be used with other AWS services like CloudFormation, Elastic Beanstalk , CloudFront, ELB, etc. It uses AWS managed Certificate Authority by AWS to provision public Certificates. See TLS Certificate Authorities for general background on CAs.
Can be used to create single, multiple, or wildcard certificates.
You can also create a Private Certificate Authority and issue private certificates.
Third party certificates can also be imported to ACM.