The process of changing verbs into their corresponding nouns is known as nominalization. Academic writing frequently uses nominalizations; that is, the noun forms of verbs. Nominalisation shifts the focus from action to concepts

For example:
We walked for charity.
The verb 'walked' has been nominalized to the noun 'walk'.

The charity walk.
As you can see from the example above, when a verb is nominalized, it becomes a concept rather than an action.

For example,
We walked for charity. We raised money for the Leukemia Foundation.
This sentence will change into :
The charity walk raised money for the Leukemia Foundation.

Some more examples of nominalization are:-

The crime was increasing rapidly and the police were becoming concerned.
This sentence will change into:
The rapid increase in crime was causing concern among the police.
The verb increasing has been nominalized to the noun increase.
The verb was becoming concerned has been nominalized to the noun concern.

Let us take another example

Germany invaded Poland in 1939. This was the immediate cause of the Second World War breaking out. This sentence will change into: Germany's invasion of Poland in 1939 was the immediate cause of the outbreak of the Second World War.

The verb invaded has been nominalized to the noun invasion.
The verb breaking out has been nominalized to the noun outbreak.

Read More: Degrees of Comparison of Adjectives: English Grammar