Difference between invoking thread.start() and thread.run()

Consider following thread example written in kotlin

fun main() {

    val thread = Thread {
        for(i in 0..10)
            println("Hi Am Thread0 ${Thread.currentThread()}")
    }

    println("Start ")
    thread.start()
    println("Finish ${Thread.currentThread()}")
}

Above output looks like below,

Start
Finish Thread[main,5,main]
Hi Am Thread0 Thread[Thread-0,5,main]
Hi Am Thread0 Thread[Thread-0,5,main]
Hi Am Thread0 Thread[Thread-0,5,main]
Hi Am Thread0 Thread[Thread-0,5,main]
Hi Am Thread0 Thread[Thread-0,5,main]
Hi Am Thread0 Thread[Thread-0,5,main]

if we change thread.start() to thread.run(), then output looks like below,

Start
Hi Am Thread0 Thread[main,5,main]
Hi Am Thread0 Thread[main,5,main]
Hi Am Thread0 Thread[main,5,main]
Hi Am Thread0 Thread[main,5,main]
Hi Am Thread0 Thread[main,5,main]
Hi Am Thread0 Thread[main,5,main]
Finish Thread[main,5,main]

Now, difference is very clear by observing thread name???…