Internet FOUM is a web application for holding discussions and posting user generated content. Internet forums are also commonly referred to as web forums, message boards, discussion boards, (electronic) discussion groups, discussion forums, bulletin boards, fora (the Latin plural) or simply forums.

FORUM

Online chat can refer to any kind of communication over Internet, but is primarily meant to refer to direct one-on-one chat or text-based group chat (formally also known as synchronous conferencing),

CHAT room

(quotaions from WIKIPEDIA)