What does building power mean?

Hi, by building power and total combat power in researching technology you can calculate the points in daily challenge. For example: building power level 9: 20 and building power level 10: 25 , so 25-20=5*1000=5000 points that you can earn in daily challenge. It’s same in research technology

Building power is earned from adding and upgrading buildings. It does not have a specific meaning other than that you can earn rewards from various daily challenges by increasing the power (by upgrading). You will have an overall Building Power score that adds to your Power rating for your city. Just an indication of how far you have progressed.