A gerund is a noun that has been formed by adding the suffix -ing to a verb. The gerund will often function as a verb within the clause, but in the context of the complete sentence forms a subject. Progressive active participle verbs also end in -ing, but retain verb form. Let's learn to tell the difference between a gerund (noun) and a progressive active participle (verb).
But believing ends in seeing
Caption 44, Katie Melua - A Happy PlacePlay Caption
You will be seeing them again.
Caption 37, George Orwell's Nineteen Eighty-Four - BBC TV MoviePlay Caption
In the first example, "seeing" and "believing" are gerund nouns. Try placing the definite article "the" before the words and see if the sentence still makes sense: "But the believing ends in the seeing." The fact that it works grammatically shows that both "seeing" and "believing" are gerunds. But in the second example, "You will be the seeing them again" would be grammatically incorrect, because in this case "seeing" is a verb.
I'd like your opinion about fast driving on the highway.
Caption 21, James Dean - Interview & Famous Drive Safely SpotPlay Caption
I'm in a truck, we're driving through the bush.
Caption 23, Kiting For Conservation - KenyaPlay Captio
In the first example, "the fast driving" works, so it is a gerund noun. In the second example, "we're the driving..." does not work grammatically, so it's a verb.
Try taking examples of some English verbs and adding -ing to the end of them to make the gerund nouns, then search for examples on Yabla English to see them used in a real-world context.