Within CloudWatch Logs you have your log group, this is the name of the logs and is usually named after the application the logs are being collected for. You have your log stream, this is the specific instances within an application essentially all the log streams make up the log group. You are able to set an expiration on these logs and have the data forwarded to S3, Kinesis Data Firehose, Kinesis Data Streams, Lambda, etc.
There are several sources for these logs. These can range from CloudWatch logs agent, Elastic Beanstalk, lambda, Route53, etc. CloudWatch Logs Insight is used to actually review the collected log data. You can utilize a CloudWatch subscription filter to have data sent real-time to your destination rather than manually exporting the data which could take several hours. You could use subscription filters across multiple accounts to take multiple CloudWatch logs sources and filter them all through a kinesis data firehose in one account to perform real time analytic by sending it to kinesis data analytics as an example. .