It carries the fundamental meaning of bringing something into contact with something else. This can be applied to various contexts:
* Applying a physical object: Like applying paint to a canvas, applying a bandage to a wound.
* Applying a concept or knowledge: Like applying a theory to a problem, applying a rule to a situation.
* Applying for something: Like applying for a job, applying for a loan.
The word "apply" often suggests a purposeful and deliberate act of bringing something to bear on a specific situation or object.