Anticholinergic agents are a class of drugs that block the action of acetylcholine, a neurotransmitter in the nervous system. They are primarily used to treat various conditions such as gastrointestinal disorders, respiratory issues, and some symptoms of Parkinson's disease. These agents work by inhibiting the parasympathetic nervous system, leading to a range of effects like reduced muscle spasms, decreased bodily secretions, and relaxation of smooth muscles.