Tessellations are repeating shapes that fit together without overlapping and without any gaps. Tessellations can be simple geometric shapes (for example a square) or complex shapes like animals. See more at the web site tessellations.org
Inkscape is a good tool to create tessellations.
Method One: Use of paths
Step 1. Create a perfect square by holding down the control key while using the rectangle tool.
Step 2. Use the pencil tool to draw a shape on one side of the square, making sure the line extends outside the square
Step 3. Select both the line and the square and click on Path – Division
Step 4. Select the cut out shape and hold control to move shape to other side, select both shapes and click on Path-Union
Optional Step 4a. Draw another line at the bottom and use Path-Division to cut out the shape, move it to the top and combine shapes using Path-Union. (similar to steps 2-4).
Step 5. Duplicate, change colors and arrange to fit together.
Step 6. Add extra items to the different shapes to create something interesting. Duplicate and group together to complete the tessellation.