Twitter is an sms based social media site. Users can only write 140 characters at a time, meaning one tweet. Users can tweet as much as they want. There are fake profiles or persons that have more than 1 profile.
It works best when used from a smartphone. Pictures can be directly uploaded with a smartphone, also the ability to tweet in real time on the street, on a roof, park, beach, club, bar, concert, etc. Pretty much anywhere.
To get the most of the site you are supposed to use hashtags, which is basically just putting a numerical symbol in front of the keyword you want people to find. For example "Great game of #chess". So people will find chess. You can also search hashtags, to find what people are saying in real time.