Amazon CloudWatch Logs

Official docs outline

Core concepts
Log events, log streams, log groups, retention and log classes.
Log groups and streams
Creating log groups and streams and setting retention and encryption.
Logs Insights queries
Query syntax and analyzing log data interactively.
Metric filters
Extracting metrics from log patterns.
Subscription filters
Streaming logs to Lambda, Kinesis and Firehose in real time.
Filter and pattern syntax
Matching terms and JSON fields in filters.
Live Tail
Viewing logs in near real time.
Exporting to S3
Exporting log data to Amazon S3.
Anomaly detection
Detecting unusual log patterns.
Cross-account centralization
Centralizing logs across accounts and Regions.
Security
IAM and KMS encryption for logs.
Service quotas
Log event size and API request limits.

Each section links to the official page. Titles and summaries by Extra Credit; the docs belong to their authors.