Amazon RDS (Relational Database Service) is a web service provided by Amazon Web Services (AWS) that makes it easier to set up, operate, and scale a relational database in the cloud. It allows you to choose from several popular database engines, such as MySQL, PostgreSQL, Oracle, SQL Server, and others, without the need to manage the underlying infrastructure.

Key features of Amazon RDS include:

1. Database Engine Options: RDS supports multiple database engines, which means you can select the one that best fits your application’s requirements.

2. Automated Backups: RDS offers automated backups with user-defined retention periods. You can also take manual snapshots of your database.

3. High Availability: RDS supports Multi-AZ (Availability Zone) deployments, which automatically replicates your database to a standby instance in a different Availability Zone for enhanced availability and fault tolerance.

4. Scalability: You can easily scale your RDS instance vertically by changing its instance type or horizontally by using Read Replicas (for read-heavy workloads) or Sharding (for write-heavy workloads).

5. Security: RDS provides security features like encryption at rest and in transit, IAM-based authentication, and network isolation through Amazon VPC.

6. Monitoring and Metrics: RDS allows you to monitor the performance of your databases using Amazon CloudWatch and provides insights into metrics like CPU utilization, storage, and network I/O.

7. Patch Management: Amazon RDS takes care of routine database maintenance tasks, such as patching the database software, which helps you focus on your application rather than administrative tasks.

8. Easy Deployment: RDS is easy to set up, and you can launch a new database instance with just a few clicks through the AWS Management Console or API.

By using Amazon RDS, you can offload the burden of database administration and focus on building and scaling your applications. It’s a popular choice for many businesses looking to host their relational databases in the cloud due to its ease of use, flexibility, and built-in features.