Ordinary users can see only the public part of the Sandbox containing all the posts that did not passed the moderators' check and which authors still awaiting for invitation. However, any user who has a free invitation can invite the author of any of the post published in the Sandbox and then it will appear on the main page.
The main stream of the posts applying for an invitation, falls into the moderator's sandbox, inaccessible to ordinary users. There, each material is checked for compliance with site rules resource themes and overall adequacy. To reduce the amount of unnecessary work, a number of requirements for the materials sent were invented.
Moderation will be not passed by:
Аnnouncements and press releases;
Vacancies (we have Habr Career for that);
Questions (we have Habr Q&A for that);
Tasks (we have Habr Freelance for that);
Complaints against companies and services provided;
Pieces of code without detailed explanation;
Monosyllabic materials (a couple of paragraphs or a video);
Articles that are barely related to IT topics or not related to it at all;
Posts, that violate site rules.
It is highly likely that moderation will not be passed by (or such post will be sent for revision):
Materials with a low (less than 75%) indicator of a unique text;
Publications without correctly placed punctuation marks, with smileys, with an abundance of exclamation marks, unjustified selection of words and sentences;
Poorly designed publications (see more);
Low quality translations.
The moderator needs a certain amount of time to check your post. Typically, small publications are processed within a couple of days, large articles can be checked for a week or even longer, be patient and do not terrorize the support service. Regardless of the result of the check, you will receive a letter about the verdict to the mail (if more than a week and a half passed, it makes sense to check the «Spam» folder in the mailbox specified during the account registration).
There might be 3 results of a check:
The moderator liked the post and after making corrections to the design (if necessary), he issued an invitation for it. In this case, the author's account becomes full, and the publication immediately appears on the main page of the site. Sometimes, before sending an invitation, the post is sent back to the author for revision, for example, if images are not displayed in it or if there is not a piece of text in meaning.
The moderator found the post potentially interesting and moved it to the public part of the Sandbox, leaving the decision on issuing an invitation to the users of the site. It's not a fact that one of the users will decide to invite you, so, as an option, you can try to send another post to the Sandbox.
The moderator rejected the post. In this case, you will receive a notification letter to the mail with the reason for the refusal, and you will again have the opportunity to send a new or carefully edited article to the moderation. Re-sending the rejected article is not necessary, no less than complain to the support team about the injustice of the decision.
Here is how Sandbox works:
Pay attention if the material proposed in the Sandbox is rejected, we no longer store the text, so copy important information on your storage in advance.
As you can see, the Sandbox is not as scary as you could be told.