If you want to see your colleagues information, change level at the top left of the screen. Below you user photo there is a dropdown, open that to select to see another user, a whole department or the entire company's information. All dependant on what user rights you have.

On Accounts, Contacts and Opportunities it's possible to be several users connected. Any connected user will get the shared Account, Contact or Opportunity displayed in the personal lists. If you are connected to a shared object each user will be notified on the smartphone on any add/delete/change that has been done by the other users on the shared object.