A jinja is a Shinto shrine. Jinja house kami,and ceremonies are performed there. The architectural style of jinja is different from Buddhist temples. When you visit a jinja, you pass through a gate called a torii, indicating that you are about to enter sacred space. The jinja lies inside that sacred space.
Japanese people usually visit jinja during seasonal events and to receive blessings. People also come to pray to the kami for their happiness, success, good fortune, etc.