Adding to what someone else replied to you, it also can mean "bump to the top" of your PING list. Whenever you post a reply, it is added to your Ping list (private replies are not). Usually when I quickly glance through an article that I would like to save for later viewing, I will reply "bttt", "bump for later", or just plain "bump".
And don't think of it as ignorance. It's a learning curve. Trust me, I didn't get it right away either. Also, in your Search browser, enter "posting help" or "HTML"...it'll explain how to do italics, bold, underline, different font colors, et. al.
Thanks for that! I've wondered about how to use different fonts, italics, etc. Now I know where to look. Many thanks.