First of all logging is really important, and are a critical part of any system, they will give you insight into what a system is doing as well what happened.
Virtually every process running on a system generates logs in some form or another. When your system grows to multiple hosts, managing the logs and accessing them can get complicated.
Searching for a particular error across hundreds of log files on hundreds of servers is difficult without good tools.
A common approach to this problem is to setup a centralized logging solution so that multiple logs can be aggregated in a central location.