time.sleep — sleeps thread or process?

import time
from threading import Thread

class worker(Thread):
    def run(self):
    	for x in xrange(0,11):
    		print x
    		time.sleep(1)

class waiter(Thread):
    def run(self):
    	for x in xrange(100,103):
    		print x
    		time.sleep(5)

def run():
    worker().start()
    waiter().start()

>>> thread_test.run()
0
100
>>> 1
2
3
4
5
101
6
7
8
9
10
102