Direct cost: include dedicated labor, material, supplies, equipment, licenses, fees, training, travel, or professional service fees - [Applied directly to THIS project]

Indirect cost: Example, if a color printer is shared by several project teams, it’s difficult to definitively determine what percentage of costs each should share.

Variable cost: fluctuate and can't be predicted with absolute certainty. For example, travel or transportation costs that can change depending upon the cost of fuel or  certain commodities and types of raw materials.

Fixed cost: are static throughout the project or have only a small likelihood of fluctuation. Fixed costs are usually for items such as rents, leases, licenses, salaries, and fixed fees
 

regards

CN Patil