More information is available at the community portal. You may ask questions at the help desk, village pump or on IRC channel #wikimedia-commons (webchat). You can also contact an administrator on their talk page. If you have a specific copyright question, ask at the copyright village pump.
Wikimedia Commons has a specific scope
Thank you for your contributions. Your image or other content, File:Innostahl_Rostock.jpg, was recently deleted, or will soon be deleted, in accordance with our process and policies, because it was not, or is not, within our scope. Please review our project scope, but in short, Commons is targeted at educational media files including photographs, diagrams, animations, music, spoken text and video clips. The expression “educational” is to be understood according to its broad meaning of “providing knowledge; instructional or informative”. Wikimedia Commons does not contain text articles like encyclopedia articles, textbooks, news, word definitions and such. Each of these other kinds of content have their own projects: Wikipedia, Wikibooks, Wikisource, Wikinews, Wiktionary and Wikiquote.
If the content seems to fit the scope of one of those other projects, please consider contributing it there. Otherwise, consider an alternative outlet. If you think that the deletion was in error because the contribution really was in scope, you can appeal it at Commons:Undeletion requests, giving a reason why it fits our scope to help others evaluate the matter. Thank you for your understanding.