Final answer:
The term that refers to an online forum where people and companies post their thoughts and other content, usually related to a narrowly defined topic, is a blog.
Step-by-step explanation:
Blogs are online diaries or journals where individuals, groups, or companies can share their views, news, or other information on specific subjects. As with the writers' forum mentioned, these forums often start with a focus on a particular subject but can evolve into communities where various topics are discussed.
Moreover, social media platforms have become significant forums for information and discussion, rapidly influencing public opinion and decision-making. While social media posts can range widely from sports to entertainment to lifestyle, blogs often have a more narrowly defined theme with space for audience interaction through comments and discussions.