A .PNG (Portable Network Graphics) file is a raster image format, which means it is made up of pixels (tiny coloured squares arranged in a grid).
Lossless compression: Keeps all image data without sacrificing quality when saved.
Supports transparency: Allows parts of the image to be fully or partially see-through.
Good for web graphics: Especially icons, diagrams, and images that need clear edges or transparent backgrounds.
Photos with many gradients (JPEG is usually better for those).
Print at large sizes (because scaling up makes the pixels visible, unlike vector files).
Analogy:
Think of a PNG like a mosaic made of coloured tiles. You can’t enlarge the mosaic without seeing the edges of each tile.