Consider the retweet.
It's such a simple act. Someone on Twitter writes something, and someone else reads it. And thinks - hey, this is too good to not be read by everyone I know! I gotta share this with them!
And thus, the retweet button is used.
Some use this sparingly, thinking that there is an art to selecting what to retweet. That it is not an act to be undertaken lightly, and that ample preparation and deliberation is mandated before one commits oneself to it.
Others have a more direct approach.
Now, consider the fact that we all know different people. Those present in your life are most likely not present in mine, and vice versa. What I see in your timeline is not what you see in yours, and what you see is not what I see.
Good thing we have a way to bridge that gap, isn't it?
If we take a step back, we can see that there are more people in the world than you and I. There are, in fact, many people in it, and none of them really see eye to eye. In fact, it is a topic of intense philosophic dispute whether two people who behold the same given object really see the same thing. And thus, there is a great need for bridge building in the world.
It's a big world. And there's a lot of people in it. We're gonna need a lot of bridges.
Or, perhaps not. Remember that thing about Kevin Bacon? About how you (whoever you might be) need only to make six lateral social jumps in order to get to the aforementioned Bacon?
The same goes for retweets. Something writes something, someone else retweets - and in five more jumps, the whole world has seen you smile.
That, my friends, is power. At your fingertips.
Use it wisely. And use it often.