Each and every individual interprets information slightly diferently - through their own unique lens.
The Lens from which we observe and understanding information contains a collection of filters. The filters are reflections of our personality - the things that have made us who we are. Filters are created by our past; including the way in which we were raised, if we our religious or not, how we were educated, our personal values, morals and so on. Whilst the filters are normally a useful tool, they can also distort the way in which we interpret information - especially when that information is foriegn to us, unexpected, or unusual.
When learning to understand another persons culture the first step is to become aware of your own personal filters, understand how these may influence your judgement for the worse, and then learn how to mitigate against them.
The most common filters which cause problems in understanding another individuals culture our bias, perception and memory.