Rangi and Papa are two very important people in the Maori culture. They are actually not people, but rather they represent the sky father (Rangi) and the earth mother (Papa). Imagine that Rangi is like the ceiling of our house, and Papa is like the floor. They are so big that they cover everything around us.
A long time ago, Rangi and Papa were once together and nothing existed except them. But they were so close that their children, who were also important gods, couldn't live between them. So the children decided to push their parents apart so they could create more space. This is why we have the sky above us and the earth below us.
Every time it rains, the Maori believe that Rangi is crying because he misses Papa, and his tears are the raindrops. But don't worry, because the Maori also believe that Rangi and Papa still love each other even though they are apart. They say this is why we have beautiful rainbows because the colors represent the love they have for each other.
So, when the Maori talk about Rangi and Papa, they are talking about the sky and the earth which are very special and important to them.