There are several kinds of log on and each one is suitable to monitor a different aspect of the service.
Each family of logs owns its page that explains the details, but as a general introduction we can state that the Static Logs are the ones written after an eventĀ took place. The Live Logs are about the living status of accounts and trunks. The Log's Retention is a policy definition, more a setup than a log itself even if it's possible to download the logged data as well.