.. Once those who are interested, click on to this 'link,' {see, below}, there are additional links, on the left side of page, which.. along with the main 'body' of their info., gives a detailed explanation of what they're all about.
.. Incidentally, this is.. 'imho,' the one corr. chess site, that is designed {if you will}, for those who are looking for the least number of 'screwups'; of which, even if it refers only to the competitors; Every game 'Web'-site, has at least a few! http://iccf.com