Check this link:
force:recordData Provides the ability to create, read, update, and
delete Salesforce records in Lightning. A force:recordData component
defines the parameters for accessing, modifying, or creating a record
using Lightning Data Service.
These tags are to be used by lightning data service for providing showing,editing,creation of sobject type of functionalities
Can these tags be used in community ?
Lightning data service is currently in beta is only available for lightning experience and salesforce1. Its not available for Communities.
Read this link for more details.
Lightning Data Service is only available in Lightning Experience and
Salesforce1. Using Lightning Data Service in other containers, such as
Lightning Components for Visualforce, Lightning Out, or Communities
isn’t supported. This is true even if these containers are accessed
inside Lightning Experience or Salesforce1, for example, a Visualforce
page added to Lightning Experience.