"薬局" means a "pharmacy" or "drugstore," a place where you can buy medicine, get prescriptions filled, and often purchase other health-related products. It's where pharmacists work.

薬を買うことができるお店、つまり薬屋やドラッグストアを指す言葉です。薬剤師がいて処方箋の薬も受け取れます。