What are "Observation Pages" in Passport?

Observations made in the passports are usually referred to the additional information/corrections made by the authorities on the passport pages other than the front and back pages of the passport. Say when you got your passport, your spouse name field in blank and later when you wish to add the spouse name, you may get an endorsement inside the passport. Similarly, if there is a typo in address field, parent's name etc, usually an endorsement is made with the corrections. Its not done on cover pages, but in any of the blank pages in the passport. Also police clearance is also given as endorsements in passport. All those are refferred as observations in passport. Its not the stamps you get when you enter/exit thru airports.