ref – https://learningenglish.voanews.com/a/understanding-the-past-participle/5578371.html

We can use passive voice when we do not know who or what performed the action or when identifying the performer is not important.

In English, the most basic passive voice is formed with be + past participle. Let’s examine the bike example:

My bike was stolen.
Here, the verb “be” appears in the past tense “was.” And “stolen” is the past participle of “steal.”

Listen for be + past participle in this next example:

The dish is cooked over an open fire.

Here, the verb “be” is in the present tense “is.” “Cook” is a regular verb, so its past participle is “cooked.”