Ok so now you think I’m off my trolley – but really I’m not, think about it.
If I put this into an easy to understand scenario for you (I’m not being patronising here ok?)
You have developed a leak, water is pouring through your ceiling and you need to stop it ruining your carpet…Or any other time you might need to move a quantity of water; but you have no bucket, bowl, basin etc (bear with me). So you grab the only thing you have to hand a colander (no not a calendar 
)You fill your colander with water and take it to the sink (for instance) to empty, and surprise it’s already empty apart from a few dribbles of water…I know and you know that this is because a colander is designed to let water drain through! So it’s done its job.
If you are sending out messages on Twitter and are not using something to allow the messages to be caught they will also drain through the holes of your colander! So if you need to direct your message at a particular person or group of people you have to use the hook designed to allow their messages to be caught ‘@’ – this simple symbol comes with its own little hook ‘@’ this makes it very easy to remember.
Include a hook ‘@’ then the user name and the message will get caught in their personal feed, so they can see you have mentioned them or directed a comment at them.
Another symbol not always readily understood to new users of Twitter is hash # and in particular #FF.
The hash # symbol is to allow particular subjects/ trends to be followed easily by other people, so #thenwcalendar is showing a trend about the recent charity calendar that I took part in, and if you complete a search starting #thenwcalendar it will bring up all of the conversations going on, on Twitter about that subject.
#FF is Follow Friday – this has been started to offer a thank you to the people mentioned in the #FF list that has been generated by that user. It is thank you, this person is interesting, this person is worth following, help this person out, they’ve helped me out (you get the idea) but for the thank you to be properly registered, the earlier rule applies – you must attach a hook ‘@’ or the person mentioned will never know.
You may as well open a giant door into ‘cyberspace’ and shout from the doorway in to the darkness if you do not use a hook – unless the person you want to hear the message is on-line at that precise time, the message will float away into ‘cyberspace’.