Resolution tells you how much image data is available for a specific print size. A file that looks fine on a laptop can still fail in print because it does not contain enough detail for the dimensions you need.
The practical rule
For most print jobs, 300 DPI at final size is the safe baseline. Large-format work viewed from farther away can sometimes drop lower, but small products and close-viewed prints should stay near that standard.
What low resolution looks like
Edges soften, textures break apart, and typography starts to fuzz. These issues become obvious in print even when they looked acceptable in a thumbnail or small screen preview.
Before exporting, always check pixel dimensions against final output size. That one habit prevents a large share of beginner print mistakes.