How is watercolor made? how is it applied? what makes watercolor unique?

Watercolor is a mixture of water with gum arabic, which are usually applied to paper. Watercolor is applied in layers, applying the lightest colors first, and then adding the darker colors. Watercolor is unique because it cannot be painted over, such as an artist could if he/she was using oil, tempera, or acrylic.  

renascimento comercial, que, a partir do século 11, inaugurou definitivamente a baixa idade média, que se estenderia até o século 15.

how is this a question?