Parallel publishing is green open access, often called self-archiving, when a publication which has been published in a closed channel (subscription journal or print only) is also made openly available in an open archive or repository by the author. It's free for the researcher and the organization and it meets the requirements of funders and the Ministry of Education and Culture just like full open access publishing in an open access journal.
That depends on the publisher's policy. In the vast majority of cases, the publisher allows the author to parallel publish some version. You can check the policy in the publisher's website or in the publication agreement which you entered either at the point of submsssion or acceptance. Search terms: "green open access", "open access policy", "self-archiving", "sharing", "repository policy", "author's rights". Artur is what is called an "institutional repository".
Which version can I parallel publish?
An embargo period of for instance 12 months means that the publisher does not allow open parallel publication until 12 months have passed after original publication. In Artur, you can upload your fulltext before the embargo has expired - just mark the embargo end date in the calender which appear when you've uploaded your fulltext, and then the file will become available automatically only at that time.
In the SHERPA/RoMEO database, you can check the copyright and parallel publishing policies of journals or publishers. You will find specific details on which version of your publication you are allowed to self-archive and whether there is an embargo or not. The service is provided by Nottingham University.
The majority of publisher's (ca 80 %) approve of self-archiving of articles in universities' institutional repositories.
Network, share publications, follow your colleagues' latest activities... keep an online cv.
NB! Before you share publications, check the publisher's policy. Also note that the terms of service are note suitable for everyone.