The Scratch project format (.sb or .sb2) can only be read by the Scratch editor. Compiling a scratch project can convert it to another format that can be opened without scratch. Compiling was a popular suggestion for Scratch 2.0, However, it wasn’t added in the normal online or offline editors. To get around this, several Scratchers have made ways to turn them into more widely known formats such as exe and app.
See on wiki.scratch.mit.edu