AI/ML NN vs. VBG

Definition of VBG (Verb gerund or present participle)

Verbs ending with -ing, called gerund forms of verbs, can function as nouns (called verbal nouns), and it exhibits the ordinary properties of a noun. Though derived from a verb, a verbal noun is strictly a noun, and it exhibits nominal properties: 

It takes determiners like the and this;

It permits adjectives (but not adverbs);

It permits following prepositional phrases (but not objects);

And it can even be pluralized if the sense permits.

Examples:

Shooting paintballs is not an art form.   Shooting is a noun. 

Humor is laughing at what you haven't got when you ought to have it.   Laughing is a noun. 

In contrast, a verb gerund is still a verb, and it exhibits ordinary verbal properties, such as taking objects and adverbs.  Notice the difference in the following example:

Examples:

In football, deliberately tripping an opponent is a foul.      (VBG)     

Tripping is a verb gerund form because there is no determiner the before it

In football, the deliberate tripping of an opponent is a foul.  (NN)

Here the verbal noun tripping takes the determiner the, the adjective deliberate and the prepositional phrase of an opponent, but it exhibits no verbal properties at all.

Examples:

The building of the British Empire may be said to have begun with the ascent of Queen Elizabeth to the throne.

His acting of the part of Othello was distinguished by a breadth and grandeur that placed it far beyond the efforts of other actors.

The dead might as well try to speak to the living as the old to the young.

In conclusion, Verb gerund and verbal nouns sometimes can be fuzzy because they appear in a same -ing form, a simple rule is to check 

Whether a token follows after determiners like "a", "an", "the", "this", or adjectives (not adverbs). If it does, it is a noun (verbal noun); 

Whether a token is followed by a prepositional phrase (but not object). If does, it is a noun (verbal noun);

Whether it can be pluralized if the sense permits. If does, it is a noun;

In other cases, it is more likely a verb (gerund verb). 

references:

https://sites.google.com/site/partofspeechhelp/home/nn_vbg