I had a quick look though just now, it appears it is a way for you to efficiently submit your work to publishers for 'exposure'. You give your work away for free, they credit you in their publication, and you hope to get commission work in the future from the exposure. For anyone that maybe reading the publication and likes your style, they may contact you for commission work. And/or you save a tear sheet and plug it in your own marketing efforts, ie your website, and say you have been published in "GQ" or "Real Simple", etc. Being able to say you've been published in a big publication can be a helpful in getting perspective clients for commission work.

Under their pricing page, both you the content creator and the publisher both pay this website to be on their platform. 

Giving your work away to large publications for free for exposure is not uncommon. Though of cause one would only do it if there is a need for exposure. Exposure would be good for someone just starting out and is still building out a name. 

I looked through their list of current publishers, it is almost entirely of no-name brands. Thinking through it some more, big publishers probably don't really need free work and it may not make sense for their work flow. Meaning the inconsistency in quality of free work would actually make it quite expensive in human labor to deal with for a publisher, versus just hiring pros like they have always done. With pros, they know what they are getting, and they get want they want in the time frame that they want.

The equivalent of paying to work a "glory hole" to "blow di$*s",
in the hopes of becoming a full-time prostitute one day.