Amazon Certificate Manager can be used to easily create SSL/TLS certificates that can be used with other AWS services. The SSL certificate from ACM is free to use and the users are only charged for the services it is used with. For example, if a website is hosted on EC2 and SSL is used from ACM, the customer is only charged for using EC2.
SSL and TLS certificates allow web / mobile browsers to identify and establish an encrypted link between the server and the browser. It tells the client that the server is who it claims to be. Search engines like Google gives additional points for SSL based websites.
ACM makes it very easy to create a SSL certificate that can be easily used with other AWS services like CloudFront, ELB and more. ACM certificate are renewed automatically taking the hassle away from the customer and the SSL validation can be performed by email.