Amazon ElastiCache vs Ramfs in Linux

I am new to Amazon Web Services. I was reading about Amazon ElastiCache and wanted to clarify if it is like (may be more than that) using RAM filesystem in Linux where we use a portion of system memory as a file system. As I referred AWS documentation it says ElastiCache is a web service. Is it like an EC2 instance with few memory modules attached? I really want to understand how it exactly works.

Our company has decided to migrate our physical servers into AWS cloud. We use Apache web server and MySQL Database running in Linux. We provide a SaaS platform for e-mail marketing and event scheduling for our customers. There is usually a high web traffic to our website during 9am-5pm on weekdays. I would like to understand if we want to use ElastiCache service, how it will be configured in AWS.? We have planned two EC2 instances for our web server and an RDS instance for the database.

Thanks.