Hello Sophia,
I will try to answer to your question about what OpenACS is: it is a framework for building web applications, that is, a collection of software tools that make "easy" (to a programmer skilled in web technologies) the construction of community based websites. Its runs on a webserver called Aolserver or Naviserver (different branches of what used to be the same software) and uses PostgreSQL as DBMS.
Other examples of frameworks similar to OpenACS that come to my mind are Plone and DJango, both for the Python language, or Meteor for Javascript. OpenACS uses the Tcl language instead (and one of its object oriented extensions, XoTcl).
OpenACS has a long tradition, dating back to 1995 when it was born as a company driven project in the United States. Its market share changed during the years and currently it is quite of a niche platform, but with solid poles of activity. To my knowledge, the most active ones are in Austria, South America and Italy. Its most common fields of applications are e-learning and ERP systems, but some (including myself) also develop some personal websites.
The reason why you found a bit difficult to start using OpenACS is that it doesn't show very much "out of the box". One should start developing something using the many commodities it offers, or install a package. Unfortunately, not many wizards exist to help you do so. Also, documentation intended for beginners, the one that usually "takes you by the hand" in your first steps in other projects, sometimes is lacking or outdated. OpenACS has a very clever built-in documentation system, but it supposes at least basic familiarity with the platform.
The best place to look for support is this forum, where response is usually very solicit. If you were looking for a software like this for a specific need, you could share it with us and people could give you more targeted advices.
I hope to have answered to your question
All the best
Antonio
