Beats is a platform of open source lightweight data shippers. Its role is complementary to Logstash. Logstash is a server-side component, whereas Beats has a role on the client side. Beats consists of a core library, libbeat, which provides an API for shipping data from the source, configuring the input options, and implementing logging. Beats is installed on machines that are not part of server-side components such as Elasticsearch, Logstash, or Kibana. These agents reside on non-cluster nodes, which are sometimes called edge nodes.

Many Beat components have already been built by the Elastic team and the open source community. The Elastic team has built Beats including Packetbeat, Filebeat, Metricbeat, Winlogbeat, Audiobeat, and Heartbeat. 

Filebeat is a single-purpose Beat built to ship log files from your servers to a centralized Logstash server or Elasticsearch server. Metricbeat is a server monitoring agent that periodically collects metrics from the operating systems and services running on your servers. There are already around 40 community Beats built for specific purposes, such as monitoring Elasticsearch, Cassandra, the Apache web server, JVM performance, and so on. You can build your own beat using libbeat, if you don't find one that fits your needs.

We will explore Logstash and Beats in Chapter 5, Analyzing Log Data, and Chapter 6, Building Data Pipelines with Logstash.