If you are talking about the "Verified" tag on top its usually only for the VIP's and Celebrities to verify that they are the actual ones and not someone else.
Yeah, not to be repetitive, but "verified" is not something any old account can obtain. It is for people who have enough fame that other twitter users would want to create a look-alike account and try to act like this person. Verified is just a way to know that the tweets you are reading are in fact from a famous person and not someone posing as that person.
here is more info from twitter themselves http://twitter.com/help/verified Who has a 'Verified Account' badge? We're starting with well-known accounts that have had problems with impersonation or identity confusion. (For example, well-known artists, athletes, actors, public officials, and public agencies). We may verify more accounts in the future, but because of the cost and time required, we're only testing this feature with a small set of folks for the time being. As the test progresses we may be able to expand this test to more accounts over the next several months.
For General Public/User No need to verified Twitter Account but if you are a celebrity and want to verified as a celebrity account just hit on verified then give them necesarry proof
I only observed the verification tags on Celebrity Profiles only! i think twitter should implement necessary development for Business Professionals in different industry