title: What is a partition leader in Apache Kafka?
body: <p>Are kafka leaders partitions themselves or are they brokers?
  My initial understanding was that they were partitions which acted as read/write agents which then deffered their value to ISRs.</p>
  
  <p>However recently I have been hearing them mentioned as though they happen at the "broker" level, hence my confusion.</p>
  
  <p>I know there are other posts which aim to answer this question, but the answers there did not help.</p>