A solution stack is like a set of pieces in a puzzle. It's made up of different components that all fit together to form a complete picture. Each piece works together with the other pieces to create a complete system.
For example, if you were making a website, you would need several pieces of software and other things that all work together to create the final product. The solution stack would include all of the pieces you need. It might include software like a web browser, a database, and a programming language, as well as hardware like servers and a network. All of these pieces work together to create the website that you wanted.