Proto-Albanian language is the very first form of Albanian language that people spoke a long, long time ago. It's like when you first started to learn how to speak, you made sounds to communicate your wants and needs. Proto-Albanian language was kind of like that, but it was spoken by people who lived in ancient times, before we had written records of their language.
Just like you and your friends might speak the same language but have different ways of saying things or different accents, Proto-Albanian language had different dialects spoken by different groups of people. But eventually, all these dialects were combined and became the Albanian language that we know today.
We don't have any written records from the time when people were speaking Proto-Albanian language, so it's hard for us to know exactly what it sounded like. But we can make guesses based on other languages that are related to Albanian, like Latin or Greek, and on the things we know about the culture and history of the people who spoke it.
Even though Proto-Albanian language doesn't exist anymore, it's an important part of Albanian history and culture. People who study linguistics or Albanian history can learn a lot about it and try to understand how it influenced the development of the Albanian language that we use today.