This is about how to configure elasticsearch, logstash, kibana together to visualize and analyze the logs. There are situations when you want to see whats happening on your server, so you switch on your access log. Of course you can tail -f from there
This is about hot to configure logrotate tool, for your access/error log. A log is a record of some kind of activity which is usually maintained to track or analyze that activity. An access log is a record of the activities on your server.
Nginx is widely used as a front-end proxy server to php server which means that when a client makes a request, nginx receives them first and then sends them to php(back-end) server to process them. Nginx has got ability to handle as much as 10000