Your personal account is completely private for yourself. By switching to a team account you can share (signed) documents and templates with team members. The team account also offers the option to add your own branding and additional settings like a landing page, font type, default message and default subject line. In addition, you can define which type of signatures are allowed to be used (typed / drawn / uploaded images).
It is by the way possible to start a branded 'team' account with just one user.
You can easily switch between your accounts by opening the menu and selecting your preferred account as shown in the image below.