Answer
A job queue is where you submit jobs to be run, and AWS Batch pulls jobs from the queue based on priority and available compute resources, while a job definition specifies how a job should actually run, including which Docker container image to use, how much memory and vCPU it needs, and any environment variables or command overrides required for that specific job.
aws batch register-job-definition --job-definition-name my-job-def --type container --container-properties '{"image":"my-repo/batch-job:latest","vcpus":2,"memory":4096}'Real-world example A video processing company defines a job definition specifying the Docker image and resource requirements for transcoding video files, then submits thousands of individual transcoding jobs to a job queue, letting AWS Batch manage execution order and resource allocation.