What does a controller do? Finance Division: controller

Hi folks,

I will interview with Morgan Stanley with a position named Finance Analyst (Summer) (Controller, I assume). The job description seems like a mid-back office position. "Provide reporting and analysis to Business Units, Senior Management and Regulators" and "Continuously improve or enhance processes for increased control and/or efficiency". Does anyone have some insights related to the job? Like the general responsibilities (or a typical day) held by a controller. And what does it mean by control?

Many thanks for the help.