Judging by your question i'm going to go under the assumption you have an average level of battery understanding.
Watt hours(WH): It's not a standardized measurement unit so your not going to see it everywhere. You are far more likely to see mah(milli-amp hours) It's the total amount of electricity that you can pull from the battery. 1 WH is the amount of energy it would take to provide 1 watt of energy for an hour. 10 WH is 10 watts of energy for 1 hour. 10WH is also 1 watt over 10 hours, or 2 watts over 5 hours. To answer part of your question, yes, the bigger the number the longer your battery will last.
It's impossible here to say how long that will last. There are far too many variables. Various things that will affect your battery life are screen brightness, wifi on/off, plugged in peripherals, battery age. Even the temperature of your room will affect your battery life.