What it means? "Everybody understood, Only I have not understood!!!"

Dear Friend, Often we are all in a situation where - "Everybody understood  and  I have not understood". Examples - 1. Go to a foreign country, where everyone is using machines, credit cards, but we have difficulty. 2. Go to a social party, everyone has some table manners, some expectations, everyone is judging others, how they walk, how they talk etc. we are uncomfortable. 3. Go to a new place, everyone is familiar with directions, place names, but we are not familiar with. 3. Go to a class say CS1100 or CS3700 or any other course etc., everyone understood something we have not understood . Now! Think about these... What is the difference between " understanding "  and  " accepting " a concept? What is the difference between "Not  understanding "  and  "Not  accepting " a concept or statement? Is it compulsory to "accept", blindly "accept"? Do real scientists "accept"...