This is an old plugin that used to be in the core, but ended up not being used that much, and was moved out. It has not been upgraded in some time. The idea is you create a page called site.cron (configurable cron: some.page), and on the page put content like the following.
3600 0 somefunc param1=one param2=two etc
86400 0 otherfunc param1=one param2=two etc
The first line will cause somefunc (a markup function) to be run up to once per hour, etc. (The second number will be transformed into a timestamp of the last time the cron job was run) The otherfunc will be run once each day. A log will be generated on page site.cron.log (configurable cronlog: some.page) of all jobs run.
To work the cron page probably needs to be publically viewable. Not sure. You can also manually trigger the cron jobs (for testing purposes) by viewing the cron page and adding cron=active or cron=demo to the url.
Note this plugin doesn't use the normal cron mechanism for triggering actions, but is rather triggered by page clicks. So if there is no traffic to your site your cron jobs will not be triggered. However for moderately actives sites, you should be able to get reasonably good approximation of cron behavior.