Beliefs are ideas that we hold to be true. For example: I believe that London is the capital city of England. I believe that this website is called AB12.
Beliefs may be stated with the words I believe in front of them or they could be stated with no such reference ie Paris is the capital city of France.
Beliefs can be about big things and little things. I believe the universe started with the big bang is a belief in the same way that I believe we are having pizza for dinner tonight is a belief.
Beliefs can be almost certainly true for example rocks are heavier than air, or they can be the subject of furious debate for example my favourite team is better than your favourite team.
Beliefs can be believed by just one person such as I believe that the poem I have just written is the best poem ever, or they can be believed by many people for example I believe that the sun will rise tomorrow.
Just because it is a belief does not mean that it is true for example we used the believe that the earth was flat, but now the poplular belief is that it is round and some folk believe that it is an oblique spheroid.
Our beliefs can change.
Saying our beliefs would probably be better stated as my beliefs as they are specific to an individual though many individuals may have the same belief in which case you could say our belief if referring to all the people at the same time.
So that could be what beliefs are, I believe it is.