A temple is a place of worship. Some places of worship have common names, such as church, mandir, gurdwara and mosque, but they are all temples because they are places of worship.
Temples have existed for thousands of years. They do not especially belong to any religion. You can think of Stonehenge as a temple because it was a monument built for worship. The Ancient Egyptians, Sumerians (with their ziggurats), Maya (with their pyramids) and ancient Greeks all built temples.
Many temples lie inside holy ground. Often the holy ground is a sanctuary where the normal world is kept away. This is easily seen in the case of the Ancient Greeks because they built many temples inside each sanctuary. The most famous sanctuary is on top of a hill in Athens, Greece, and is called the Acropolis. The biggest temple within the Acropolis sanctuary is called the Parthenon. The video takes you around this site. You can also look in any of the world religions section of the website and find modern versions of temples.