Conversos were people who used to be Jewish or Muslim, but they converted to Christianity in Spain during the 15th and 16th centuries. This was a really big deal because religion was a VERY important part of life back then.
The term "conversos" literally means "converts." When Jews and Muslims became Christians, they were supposed to give up their old religion completely and adopt Christianity as their new faith. But it wasn't always that simple.
Many people were forced to convert to Christianity because it was the law in Spain at the time. Sometimes, they converted willingly because they thought it would be the best way to survive and avoid persecution. But deep down, many of these "conversos" still held on to their old beliefs and practices.
The Catholic Church didn't trust the conversos because they weren't seen as "real" Christians. There were rumors that they secretly practiced Judaism or Islam in their homes. Some people even accused conversos of having "Jewish blood" or "Muslim blood" and that they couldn't be trusted because of that.
This led to a lot of discrimination and persecution against conversos. They were often excluded from society and faced a lot of suspicion and hostility. Some conversos tried to prove their loyalty to Christianity by becoming priests or joining the Spanish Inquisition (a group that hunted down and punished people suspected of not being true Christians). But even that didn't always help.
So being a converso was a really tough thing back then. You had to give up your old identity and face a lot of prejudice and discrimination because of it.