It’s just the total number of times that your tweets have been retweeted in a given time period. You can get this one from Klout as well.

Business Goal
If it’s important for you to reach as many people as possible with your message, this is a good metric. It’s generally good for B2C firms, as the more people that know about your product the more customers you receive. The metric shows message amplification – as the number of retweets goes up, the amount of people that see your message increases dramatically. Since the average Twitter user has a few hundred followers, retweets have the potential of reaching a lot of people. It also shows how interesting or easily sharable your message is, indicated how likely it is to spread by other mediums besides Twitter. Measuring the retweets for specific tweets would also be useful to test and try which messages are the most sticky (for this you can use tweetmeme).

How do you increase it?
You increase this by sending out messages that are useful, valuable, interesting, and targeted to your followers. Another factor is your authority – if people recognize you as a leader in your industry, they are more likely to trust your tweets and retweet them. Retweeting other people’s material (participating in the community) will also help increase your retweets by the law or reciprocity.