Combining two images and blending between the two can be done in a few steps with masks.
Illustrator elements are Vector Graphics constructed of paths and fill areas. The tools in Illustrator help us manipulate these elements. Read more in the Illustrator help file.
Tools (Found under the Help Menu> Illustrator Help> Work Area> Tools)
Tools panel overview
Select a tool
Change tool pointers
Selection tool gallery
Drawing tool gallery
Type tool gallery
Painting tool gallery
Reshaping tool gallery
Symbolism tool gallery
Graph [...]
