You have logs. Billions of lines of data. You shipped, dated it, parsed it and stored it. And you used Logstash to do it. Now what do you do with it? Now you make sense of it. See everything you want, and nothing you don't. Chart it and rank it and play with the numbers. Kibana helps you do that. Kibana is a highly scalable interface for Logstash and ElasticSearch that allows you to efficiently search, graph, analyze and otherwise make sense of a mountain of logs.

logstash is a tool for managing events and logs. You can use it to collect logs, parse them, and store them for later use (like, for searching). Speaking of searching, logstash comes with a web interface for searching and drilling into all of your logs.