It is documented to set up two cron jobs for Magento 2
*/1 * * * * /usr/bin/php /var/www/html/example/web/bin/magento cron:run
*/1 * * * * /usr/bin/php /var/www/html/example/web/bin/magento setup:cron:run
What is the difference between those both? Which one is responsible for the indexers?