Language secessionism is when a group of people who speak a certain language want to break away from the larger group that speaks a different language and form their own separate group. Just like in school, when you and your friends want to sit at a different table than the other kids because they speak a different language or have different customs.
Now imagine this in a bigger scale, like a whole country with many different languages. Some people may feel that their language is not getting enough attention or respect, or that their culture is being overlooked, and they want to create their own separate group where their language and culture is the main focus.
Sometimes this can be peaceful, like in Canada where Quebec has made efforts to preserve their language and culture through activities and education. But in other cases, it can lead to conflict and even violence, like in the Balkans region of Europe where people from different language groups fought over land and power.
In the end, language secessionism is a complex issue that involves many factors like history, culture, and politics. But the main idea is that people want to have their own space where they can speak their own language and celebrate their own culture without feeling suppressed or ignored.