Starting in version 7.16, this experimental functionality has been removed. You should use the journald input in Filebeat instead.
Beats are lightweight data shippers that you install as agents on your servers to send specific types of operational data to Elasticsearch. Beats have a small footprint and use fewer system resources than Logstash.
Logstash has a larger footprint, but provides a broad array of input, filter, and output plugins for collecting, enriching, and transforming data from a variety of sources.
For more information, see the Logstash Introduction and the Beats Overview.
Intro to Kibana
ELK for Logs & Metrics