That form is called a present participle aka gerund.
Participles are very interesting particles. They can be used to turn a verb into a noun, adjective or adverb.
e.g. past-completed participles as adjective or adverbs
- Paint : The painted door.
- Grow : A grown man.
- Bless : Blessed are the meek. /* implied descriptee noun for descriptor blessed */
- Deject: She was crying dejectedly.
e.g. present-continuous participles as adjectives or adverbs
- Run: The running dogs.
- Fly: Flying eagles.
- Kill : The killing fields.
- F*ck: The f*cking idiot.
- Flail: She ran flailingly towards her lover.
The participle form of interest to your question is present-continuous participles' transforming a verb into a noun or a noun-phrase.