Ok kiddo, so you know how Muslims believe in one God, right? Well, there are a few places that are super special and important to them because they are connected to stories and events from the early days of Islam. These places are considered the holiest sites in Islam for Sunni Muslims.
The first one is the Kaaba. This is a big black cube-shaped building in the city of Mecca in Saudi Arabia. Muslims face towards the Kaaba when they pray, no matter where they are in the world. It's said that the Kaaba was built by the Prophet Ibrahim (Abraham in the Bible) and his son Ismail. It's a really old building and has been rebuilt and renovated many times over the years. Muslims try to visit the Kaaba at least once in their lives if they can, and this is known as the Hajj pilgrimage.
The second one is the Prophet's Mosque. This is a mosque in the city of Medina, which is also in Saudi Arabia. The Prophet Muhammad lived in this city for many years, and the mosque was built around his house. The Prophet's Mosque is really big and can hold thousands of people. Muslims try to visit this mosque too so that they can say prayers and pay their respects to the Prophet Muhammad.
There are a few other places that are also considered important, like the site where the Prophet Muhammad gave his last sermon, Mount Uhud where a famous battle took place, and the city of Jerusalem where the Al-Aqsa Mosque is located.
So, these are the holiest sites in Islam for Sunni Muslims. They are important because they are connected to the history and teachings of Islam and remind Muslims of the faith's key beliefs and events.