All main verbs have a present-participial form. Just add ‑ing and you've got a present participle. Sometimes you have to drop a silent ‑e as in writing. And sometimes you double an ending consonant, as in occurring.
The present participle shows up in the progressive tenses, sometimes called the progressive aspect of a verb. The progressive tense is formed by using the verb to be and adding the present participle, as in We were winning the race.
The present participle can also form a present-participial phrase. If the present-participial verb is transitive, the phrase can have an object in it, as in winning the case.
Present-participial phrases can act as adjectives, as in the judge sitting next to the law clerk. The present participle itself can act as a one-word adjective, as in the smoking gun.
Finally, the present participle can act as a noun. When it does, it's called a gerund. Thus, an -ing phrase can act as a noun, as in He was fond of watching movies.