Middle Spanish was a way of talking and writing that people used a very long time ago in Spain. It was kind of like a different language than what we speak and write today.
Back then, people didn't have the same devices and tools that we have now, so their way of speaking and writing was different. They used words and spellings that we might not use today.
Middle Spanish started in the 13th century and went until the 16th century. During that time, a lot of things happened in Spain, like wars and new discoveries. People from different parts of the world came to Spain, so the language started to change too.
Middle Spanish was important because it is a part of Spain's history and shows how the country evolved over time. It also helped create modern Spanish, which is what we speak and write today.