What are the differences between the short run, long run, and very long run?

Short Run

A period of time in which at least one input, typically capital, is fixed, and producers can only adjust the variable inputs like labor.

Long Run

A period in economics during which all inputs and operations can be varied, allowing for the adjustment to changes in market conditions or demand.

Very Long Run

In microeconomics, a period of time long enough that technology can change and firms can introduce new products.