You have one in your home university and another in your host university. About the preparation of your stay: To make your stay, you may often look for information on the website of your host university. Be careful because maybe the information is not updated, correct or complete. Several examples: your host university is located in Madrid but not in the center but in the outside and do not realize it until you consult a map or you go there. You can also host your university has its main powers in Madrid but that other faculties are located in smaller cities outside Madrid and even 70 or 80 kilometers. If in addition to your main career follow language classes such as Chinese or Japanese, your host university may ask you to pay tuition and that is legal because it is not part of your main career.
It can also happen that the host university implements a new career. In this case, only the classes are taught the first course but on the website often to the curriculum of the entire race. That can cause problems if the subjects that interest you are solely those of supports or third (or more) because they have not taught. About the scholarships: The European Union awarded a scholarship to all Erasmus students. But the amount is very low and does not cover all expenses for your stay. Barely covers the rent for a month or at most two months. Therefore, you must have other financial support.