data manager
The transaction package wraps data managers implemented for different transactional backends, such as SQLAlchemy (zope.sqlalchemy), but also many others.
A web framework.
A retryable exception is any exception that is recognized as retryable by an active data manager. These errors usually inherit from transaction.interfaces.TransientError. These errors are temporary and thus marked as retryable. For example, a serialization error in a database resulting from concurrent transactions.
A database transaction comprises a unit of work performed within a database management system. In the context of the Pyramid documentation, "transaction" is also the name of a Python package used by pyramid_tm.