If you represent a brand - for example, writing tweets for your employer, you might not want to use your personal information in our system. We have created Brand accounts specifically for that purpose!
Generally, larger corporations sign up as Brands. Think about it like this: if the social media content you create is made in the “voice” of your company and not yours personally, you should most likely sign up as a Brand.
When you sign up, check the I Represent a Brand checkbox. You will notice some fields dim: Gender and Birthday. That is because brands are entities that do not have genders or birthdays.