AWS: Cloud platform for many tools used in software engineering.
AWS Fargate: A task launch mode for ECS task, where it automatically shuts down once a container exits. With EC2 launch mode, you’ll have to turn off the machine yourself.
AWS Lambda: Serverless function, can be used with docker image too. Can also hook this with API gateway to make it act as API endpoint.
AWS RDS: Managed databases from AWS.
ECS Task: Launch a task in ECS cluster. For long-running services, launch via EC2. For small periodical tasks, trigger via Cloudwatch. For the latter, think of cron-like schedule for a task. Essentially at specified time, it runs a predefined docker image (you should configure your entrypoint.sh accordingly).
Terraform: Infrastructure as code tool, essentially you use it to store a blueprint for your infra setup. If you were to move to another account, you can re-conjure existing infra with one command. This makes editing infra config easier too, since it automatically cleans up / update config automatically.