What is the meaning of Posting?

present participle and gerund of post

The action of the verb to post.

An item inserted into a register, ledger or diary.

A message posted to a computerized bulletin board, a newsgroup, a blog, etc.

The place where a soldier or airman is posted for duty; the time spent there.

posting: a message posted to a computerized bulletin board, a newsgroup, a blog, etc.

Source: wiktionary.org