Both alfresco share and explorer are available for me from the community edition which I downloaded. How to know the version of alfresco from GUI?
In the cmis landing page. http:<your server>:<your port>alfresco/service/cmis/index.html
In Explorer - Admin Console, System Information
What is the difference between alfresco share and explorer?
Two different web based user interfaces to the alfresco repository.
I created a site and under document library, created two folders and populated some pdf/word documents. I doubt whether the search will provide us content based search on the documents in the document library or is it simply based on meta data?
There's lots of search functionality built into Alfresco. You can search on property values or "fuzzy logic" with the full text search. Equally the PDFs will be converted to text and then indexed.