Definition: The term post in the context of the Web is either a noun or a verb, depending on how it's used. If someone says that they've "posted something" on the Web, this means that they've published some sort of content (a story, a blog post, a video, a photo, etc.). If someone says that they're "reading a post", this usually means that they are reading text that someone has posted via a blog or Web site.
Examples:
"I just published a post about my cat, Fluffy."
or
"I'm posting about my cat, Fluffy, today."