Talking about SharePoint structure can be very confusing. People are talking about site collection, which in the code developers are referencing with SPSite. Nothing wrong until now, just term of “site collection” can be easily confused with SPSiteCollection, which represents all sites in a web application. So, don’t confuse these words. What we called “site collection” is more a “site”.
Another confusion is between site and web. What we called “site” has the equivalent in the code object SPWeb. So is not quite wrong if we consider “site” to be a “web”.
Here is a summary of how SharePoint is organized, starting with web application level.
- A web application contains one or multiple sites (we called them “site collections”, but don’t confuse them with SPSiteCollection). If someone is asking you question about this, I recommend you to clarify what he/she is asking about to give correct answer.
- Each site, or site collection if you prefer these words, contains at least a web, which is root web or top level site. In the code, you know it by SPWeb, which is the reason I recommend you again to clarify the question if you receive one.
- Under the top level site or root web, you can have more webs or sub-sites, which can be organized in a complex hierarchical structure.
In any possible situation you might be, I think is a good idea to clarify questions and terms. Microsoft can be very confusing sometimes, so don’t get caught in terms meaning storm.