Create a Sprite Atlas

To create a SpriteA 2D graphic objects. If you are used to working in 3D, Sprites are essentially just standard textures but there are special techniques for combining and managing sprite textures for efficiency and convenience during development. More info
See in Glossary Atlas:

1. Go to Assets > Create > 2D > Sprite Atlas.

Unity creates the Sprite AtlasA utility that packs several sprite textures tightly together within a single texture known as an atlas. More info
See in Glossary in the Assets folder, with the file extension .spriteatlas.

SpriteAtlas