What is a mahram in Islam?

One of the aspects of life covered in Islam is the interaction of males and females. Islam has developed a system of mahram and ghayr mahram - people who are not allowed to be married and those who can marry, and this system has great impact on the life of women, for instance in regard to the permissibility to travel. Maulana Sultan from the UK gives us some clear insight in this issue. Have a read.