WD-40 is a versatile lubricant and cleaning fluid. This fluid is often used to protect tools from rust, lubricate bolts that are difficult to open, and clean electronic components. 
WD-40 Function: 
Protects tools from rust
Lubricate bolts that are difficult to open
Clean electronic components
Removing fat and furious
Cleaned the sound on the hinge
Protects metal surfaces from corrosion
Provides lubrication for almost all types of equipment
WD-40 is available in cans or spray. This fluid can be used for various needs, such as in households, workshops and industry.