Fill:
fill color is used for background color.
Stroke:
stroke is used for border color.
Step 1:
Select shape
Step 2:
click on fill to set a background color for a shape.
Step 3:
click on stroke to set a border color for a shape.

Adobe illustrator Tutorials
Selection Tool
- How to draw a square with rectangle tool in adobe illustrator?
- How to zoom in adobe illustrator?
- How to resize the shape with same proportion in adobe illustrator?
- How to rotate a shape in adobe illustrator?
- How to make copies of a shape in adobe illustrator?
- How to select all shapes together in adobe illustrator?
- How to color border of a shape in adobe illustrator?
- How to select specific objects or shapes together in adobe illustrator?