Logstash Flush Logs Explanation

Hello Loggers,

I was wondering if someone could explain what the logs produced by logstash in "logstash.log" mean when you restart Logstash and there is an event flush after sending the SIGTERM to Logstash. Sample Log:

index=>"indexname-%{+YYYY.MM}", user=>"username", password=>, ssl=>true, cacert=>"/opt/logstash/some-file.pem", codec=><LogStash::Codecs::Plain charset=>"UTF-8">, workers=>1, manage_template=>true, templat
e_name=>"logstash", template_overwrite=>false, flush_size=>500, idle_flush_time=>1, doc_as_upsert=>false, max_retries=>3, script_type=>"inline", script_var_name=>"event", scripted_upsert=>false, retry_max_interval=>2, retry_max_items=>500, retry_on_conflict=>1, action=>"i
ndex", ssl_certificate_verification=>true, sniffing=>false, sniffing_delay=>5, discovery=>"zen", aws_protocol=>"https">]>, :busy_workers=>0}, {:type=>"elasticsearch", :config=>{"hosts"=>["hostname.com:9224", "hostname.com:9224", "hostname.com:9224"]

What do the following terms mean:
workers: (I believe the worker takes in multiple events from the input threads, then runs all these events as a batch to the Filter/Output)
manage_template: (I though the templates only belong to ES [Elasticsearch])
template_name:
template_overwrite:
flush_size: (Flush size in what units/metrics?)
idle_flush_time:
doc_as_upsert:
max_retries:
script_type:
script_var_name:
scripted_upsert:
retry_max_interval:
retry_max_items:
retry_on_conflict:
sniffing_delay:
discovery:
busy_workers:

Thanks In Advance,

You probably want to start here - https://www.elastic.co/guide/en/logstash/current/plugins-outputs-elasticsearch.html

Thanks!