Mosques are open to everyone. You will have to leave your shoes at the entrance and women in most mosques are required to cover their heads with a scarf and naked parts of their legs and shoulders. If you don’t have anything with you, they will give you some scarves at the entrance for free. Silence is required inside the mosques. Most of the mosques are closed to visits at prayer times. Turkiye is a secular country where religion and politics are separated, even though the population is 98% Muslim.