My mom is a janitor.
That's cool. Where does she work? Janitors work in hospitals, schools and residential accomidations. 
She works at a high school.
Does she just clean? Sometimes janitors do maintenance and securitites too.
Yes she just cleans.
. Cleaning is one of the most commonly outsourced services.
Occupational tasks.
Although most of the work performed by janitors and building cleaners is indoors, sometimes it can be outdoors. Outdoors work mainly include sweeping walkways, mowing lawns, or shoveling snow. In some facilities or buildings, a separate company may be hired to do outdoor work. Office buildings are usually cleaned when they are vacant, so most of the office janitorial staff work during the evening. The work can be physically demanding and sometimes dirty and unpleasant
Janitor
A janitor (American English, Scottish English), custodian, porter, cleaner or caretaker is a person who cleans and maintains buildings such as hospitals, schools, and residential accommodation. Janitors' primary responsibility is as a cleaner. In some cases, they will also carry out maintenance and security duties. A similar position, but usually with more managerial duties and not including cleaning, is occupied by building superintendents in the United States (and occasionally in Canada) and School Site Managers in schools in the United Kingdom