The Layers function in Adobe Illustrator lets you separate parts or elements of your graphic into virtual layers and work with the elements on the individual layers. Each layer can be modified or moved without affecting the artwork on other layers. You can create new layers and move existing design elements to them or freely move artwork from one existing layer to another. When the project is complete, you can flatten the layers into one so you can save your project to a format like JPG or PDF that does not support layers.
Open Adobe Illustrator. Click "File," then "New" to create a new project or "Open" to load an existing project.
Click "Window" and then "Layers" to open the Layers panel.
Click a layer in the Layers panel to select the layer that all layers will be flattened into. Click the Layers panel menu, and click "Flatten Artwork."