Boost is like a big box of toy blocks that help people write computer programs more easily. The blocks are small bits of code that have already been made and tested by other people, and they can be put together like puzzles to create bigger and more complicated programs.
For example, there's a block that helps people work with dates and times, so they don't have to write all of the code themselves. There's also a block that helps people work with files, so they can read and write information to and from them without having to write a lot of code.
Boost is like a big collection of these different blocks, all in one place. It makes it easier for people to write programs because they have access to all of these ready-made blocks that they can use. Boost is also really popular, so many people use it and contribute to it, making it even better over time.