JPG
JPG (or JPEG) is the universal photo format. It uses lossy compression tuned for natural images, giving you small files that look great on screens, social media, and prints. JPG has no transparency layer and progressively loses quality on each re-save, so keep an original archive if you plan to edit further.
PDF
PDF (Portable Document Format) freezes a document’s exact layout so it looks identical on every device. It is the contract, invoice, eBook, and academic-paper format of record. PDFs can hold text, vector graphics, raster images, forms, and digital signatures — but editing them outside specialized tools is painful, which is why PDF-to-Word is one of the most-searched conversions.