It is always more important to be first than second. There is more attention paid to the first person to finish a race, the person who comes first in a competition or the first thing on a list, than there is to anyone or anything that is second.
This applies to sentence structures as well. The first thing in a sentence is the most important.
The basic sentence pattern of subject + verb + object puts the focus on the subject and moves the object into third place. Look at this basic sentence:
My mum cooks lunch every day.
Where is the main emphasis? The focus of your attention is on mum because she comes first. But suppose you want lunch to be the focus. What can you do to make sure this happens?
To focus on the thing or the action we are talking about and not the person who might be doing it, we use the 'passive'. This is very easy to make. The 'present simple passive' is am/is/are + the past participle of the verb we need. The 'past simple passive' is was/were + the past participle.