Plenary session is a term

Terminology

Terminology is the study of terms and their use. Terms are words and compound words that in specific contexts are given specific meanings, meanings that may deviate from the meaning the same words have in other contexts and in everyday language. The discipline Terminology studies among other...

 often used in conferences to define the part of the conference when all members of all parties are to attend.

These sessions may contain a broad range of content from keynotes to panel discussions and are not necessarily related to a specific style of delivery.

The term has been used in the teaching profession to describe when information is summarized. This often encourages class participation.

The Congress of Vienna

Congress of Vienna

The Congress of Vienna was a conference of ambassadors of European states chaired by Klemens Wenzel von Metternich, and held in Vienna from September, 1814 to June, 1815. The objective of the Congress was to settle the many issues arising from the French Revolutionary Wars, the Napoleonic Wars,...

is an example of a "congress" that did not meet in plenary sessions.