A "promoted tweet" is a tweet purchased by advertisers who want to reach a broader group of users. Promoted tweets start out as regular, normal tweets and are promoted from there. This means they can be retweeted, replied to, and favorited just like any other tweet.

Users will see your promoted tweets at the top relevant search pages on Twitter, and they will only appear in a user's timeline if it is relevant to that user. Twitter is also slowly rolling out promoted tweets to some users, so there is a chance that some may not even see your promoted tweet.

Here are a couple of user comments regarding promoted tweets:

"The timeline is not the right place for ads or spam. Please put in some option to disable this."
"It's too bad Twitter's getting this far into the ad game. These ads are simply annoying."
"I don't mind the idea of Promoted Tweets. I know Twitter needs to make money. What I hate is how a promoted tweet consumes limited screen real estate in my searches on 3rd party apps and never go away. They should age out after a period of time."

Currently, promoted tweets should probably only be used as part of a broader market strategy. It might be best to avoid jumping on the bandwagon right away; wait for some time to pass and for Twitter to improve on what is not being received as the best idea yet.