Slacks implies pants of certain materials which are not part of a suit (jeans are not slacks, and you would not refer to the pair of trousers that came with a suit as slacks.) It is also more common to use slacks to refer to pants worn by women, while men would wear trousers.
Health care safety net providers are those that have a legal mandate or mission to offer medical care to all patients, regardless of their ability to pay, and have a substantial number of patients who are uninsured or on Medicaid.
Uninsured motor vehicle (UM) coverage is for the benefit of people who are injured or killed as a result of the negligence of the operator of an uninsured auto. This is an important protection because many people are injured in accidents with uninsured motorists despite Massachusetts laws requiring compulsory coverage.