Glossary
Seamless Tile
Short answer
A pattern image whose edges match perfectly so it can repeat infinitely.
In a seamless tile the image's left edge joins its right and its top joins its bottom perfectly. Laid side by side, no seam is visible.
It is required for ground and wall textures in game development, backgrounds in web design and fabric patterns in textiles.
Normal generation does not produce this property; the tool needs a dedicated mode. Leonardo AI and Stable Diffusion both offer one.