The isarray project provides a polyfill for the `Array.isArray` method, enabling developers to check if a value is an array in older browsers and deprecated Node.js versions that don't natively support this functionality. It's designed for developers working on projects that need to maintain compatibility with legacy environments while still using modern JavaScript features. The package is particularly useful for Node.js developers and those using bundlers like Browserify to ensure consistent array checking across different runtime environments.