An EJB object and bean class are typically used interchangeably to refer to the actual logic implementation for an EJB. Prior to EJB 3.0, the ultimate base interface for any EJB (Session or Entity) was the EJBObject interface.
An EJB server is a container for one or more EJB containers. An EJB server manages and coordinates allocation of EJB application resources, J2EE naming functionality, communication with remote resources, etc. An EJB container manages the actual EJBs including their lifecycle, object pooling, security, transactions, etc.