In these two examples we have used the two participles (highlighted) to form new verb tenses:
I was walking.
I have walked.
The present participle is usually made by adding -ing to the end of the infinitive.
We use the present particle to form the continuous tenses:
He is sleeping.
They were laughing.
The past participle is usually made by adding -ed to the infinitive:
The past participle is used to form the perfect tenses:
We have walked these hills many times.
He has slept for 18 hours!
The past participle can also sometimes be used as a noun.