When –ing forms are used to make continuous tense forms, they are called present participles. Note that present participles are often confused with gerunds. Although both gerunds and present participles look alike, they have totally different grammatical properties.
Gerunds serve the same purpose as nouns. They can be the subject or object of a verb or preposition.
Smoking is injurious to health. (Here the gerund smoking acts as the subject of the verb is.)
Singing is his hobby. (Here the gerund singing acts as the subject of the verb is.)
Present participles, on the other hand, are mainly used to form continuous tense forms. They can also act as adjectives.
They are waiting for us. (Here the present participle waiting goes after the verb be and forms the present continuous verb are waiting.)
It has been raining since morning. (Here the present participle raining helps in the formation of the present perfect continuous tense.)
Past participles are forms like wanted, broken, started, begun etc. Some verbs have the same past simple and past participle forms. Examples are:
Want / wanted / wanted
Cry / cried / cried
Start / started / started
In the case of some other verbs, the past participle form is different from the past simple form.
Break / broke / broken
Begin / began / begun
The past participle forms are used to form perfect tenses and passive verb forms.
They have left.
Someone has broken the window.
You are fired.
Active and passive meanings of participles
When –ing forms are used like adjectives or adverbs, they have similar meanings to active verbs.
Falling leaves (= leaves that fall)
A fish-eating animal is an animal that eats fish.
When participles are used like adjectives and adverbs, they have passive meanings.
A burnt child is a child that has been burnt.
A broken heart is a heart that has been broken.