Filestack is a cloud-based file management service that allows users to upload, transform, and deliver files easily. It provides a simple API that developers can integrate into their applications, enabling seamless file handling from various sources, including social media and cloud storage. With Filestack, users can perform tasks like image resizing, format conversion, and video processing. The platform also offers secure file storage and sharing options, making it a versatile tool for businesses and developers looking to enhance their file management capabilities.