What is bitcoin cryptocurrency library?

Could you elaborate on the concept of "Bitcoin cryptocurrency Library" for those who may not be familiar with the intricacies of cryptocurrency? Specifically, I'm interested in understanding its purpose, key functionalities, and how it relates to the broader Bitcoin ecosystem. I'm also curious about the technical underpinnings, such as which programming languages it may be written in and if it offers any unique advantages over other similar libraries. Your explanation would be invaluable for those seeking to delve deeper into the world of Bitcoin development.