If you open up your inventory, over to the right hand side you will see a number below the word "Damage". Similarly, if you open up your hero's page in your character profile, you will likewise see a number labeled as damage (or DPS, or something of the like). What is the difference between these two numbers?
The one that is shown in your inventory is your current damage with all the buffs that affect you(including set bonuses, mantra's, laws, shouts, followers, shrines, etc.).
The one showed on profile page is your damage without any buffs and without any set bonuses.
The profile DPS doesn't include some of the variables in the calculation, mostly just damage buffs from skills (including passive), because these damage buffs are inactive at the moment of calculation, i.e when offline (profile page treats your stats the same regardless if you're online or offline)
Sheet DPS includes all these variables, because it is calculated when you open your inventory.