Image resolution refers to the number of distinct pixels in each dimension of a digital image. A "1920×1080 pixel" image has 1920 pixels wide and 1080 pixels tall — a total of approximately 2 megapixels. Higher resolution means more detail: a 4000×3000 pixel image can be printed larger and cropped more aggressively than a 800×600 pixel image.
Resolution requirements vary by use case. For web display: a 1200px wide image is sufficient for most uses, and larger images just increase page load time. For social media: platforms have specific recommended resolutions (Instagram posts: 1080×1080px, YouTube thumbnails: 1280×720px). For printing: 300 PPI is the standard for sharp print — a 4×6 inch print needs at least 1200×1800 pixels.
Upscaling (enlarging) a low-resolution image doesn't truly increase detail — it just interpolates (guesses) new pixels. AI upscaling tools like FileCurve's Upscale Image can intelligently estimate missing detail with better results than simple interpolation. Downscaling (reducing resolution) always works well and reduces file size proportionally.