Material is the stuff you use to make something.
You might use cardboard to make a model house. The cardboard is your material.
If you were building a real house to live in, you would have to choose different material. Cardboard would not keep rain out. It would go soggy and your house would fall down.
For a real house, you would have to get a material that wouldn't let rain in.
The material would also need to be strong enough to hold up a roof.
Cloth would not do. It would fall down in a heap.
Plastic would not let rain in, but the sun would be shining through it, and the wind might blow it down.
For a real house that you can live in, you need materials that are artificial - materials that are made by people and not just found in nature.
Brick, cement and glass are used by people who build houses, schools, factories, shops, sheds, and any other building that needs to be safe for people or for animals.
Look at the picture of St. Michael's N.S. Crimlin. Can you see bricks? Cement? Glass? When the building was finished, it was painted. That's why you can't see bricks and cement.