Okay, so Scottish nationalism is when people from Scotland feel very proud and supportive of their country and want it to have more power and freedom. They might think that Scotland should be its own separate country instead of being part of the bigger United Kingdom of England, Scotland, Wales, and Northern Ireland.
Some people who support Scottish nationalism might say that Scotland has its own unique culture and history that should be celebrated. They might also think that decisions about how Scotland is run should be made by Scottish people themselves, instead of by people who live in other parts of the UK.
It's kind of like if you really love your own family and you think it's important for your family to make its own choices and not always follow what other families are doing. But sometimes your family has to work with other families to get things done too.
Some people who don't support Scottish nationalism might worry that splitting off from the UK could be difficult and cause problems for both Scotland and the rest of the UK. They might also think that it's good for different parts of the UK to work together and share resources.
Basically, just like big decisions about your family might be tricky and have different opinions, big decisions for a whole country can be tricky and have different opinions too!