Boolean Operations

Boolean operations are:
• Unite
• Subtract
• Intersect
These options can be used when two or more solid bodies share the same model space in the part file. 
To use this command, go to Insert → Combine Bodies.
Consider two solids given. The block and the cylinder are next to each other as shown below. 

Unite:
The unite command adds the Tool body with the Target body. For the above example, the output will be as follows if Unite option is used.

Subtract:
When using the subtract option, the Tool body is subtracted from the Target body. The following would be the output if the rectangle is used as the Target and the cylinder as the Tool.

Intersect:
This command leaves the volume that is common to both the Target body and the Tool body.The output is shown below