@AmerigoVespucci is a tag for the person Amerigo Vespucci.

#AmerigoVespucci is a tag for people talking about Amerigo Vespucci.

@ directs a post at someone, usually someone a comment is directed to or anybody you mention. @ precedes the handle.

# is called a hashtag. It is used to identify your topics, subjects and lists so other people can find your tweets, it works like a cross-reference or an index-tag. Note the spaces at the end of what you're @ or # and the lack of spaces in the middle of @ and #. Both symbols end at the next space.

example:

@AmerigoVespucci Did you see @BarackObama 's interview with Robin Roberts where he supported #MarriageEquality ?

Some hashtags are used for lists. The only one I can recall right now is #tcot which is basically a teabagger extreme-conservative list. I generally tag all the the most offensive things I have to say with #tcot to piss off the loonies.

...thanks for confirming.

that is one of my favorite things I've read in the last 3 months.

How many other ways can you twit-spam 100000 idiots including teabagger Members of Congress, birther celebs and asshat radio-talkers with insulting anti-RW propaganda and they can't do anything about it?

I've spent the better part of a slow afternoon annoying John Boehner by making #Wherearethejobs go viral on his official Speaker of the House twitter-feed to the point it drowned out his social media staff that posts his talking points.

As I said in the OP, this is stuff I "should" know, by virtue of what I do for a living. I have a number of clients who are older and skeptical when it comes to social media. But I also remember a story from the San Jose Business Journal several years ago about a local physician who works Twitter to his advantage. He still does...I follow him. He's found the right message and has made the commitment to "tweet regularly." The most effective way to convince a client who is sitting on the fence is to share a success story. That changes everything.