There are two standard words in Russian for mother: мама, мать. The former is perfectly regular, and the latter is one of the most ancient words in the language and retains old quirks to it:

Although these words mean basically the same thing, they are stylistically different. A child would never say «Мать приготовила ужин» “Mother prepared dinner.” A child will only say «Мама приготовила ужин». Roughly speaking, children, young adults, and adults still living with their parents will usually refer to their parents as мама and папа. As they grow into later adulthood, people in their thirties and forties will refer to their parents as мать and отец. It just sounds more grown up.

Тhese are not hard and fast rules. Emotional closeness and gender influence things as well. A forty year old woman with a really close relationship to her mother may well call her мама. It is less probable that a forty year old man would do so, but it is still possible. And a twenty year old woman whose mother is a shrew may well refer to her as мать.

Sample sentences: