Answering my own question: I've always identified as an atheist but I still believe there's more to us than just atoms.

In my view, there's something in our consciousness that gives you identity and defines who you are, why you perceive the flow of time and the sequence of events that happens to a specific person (you). It's why from my perspective I'm the main character of my story and everyone else is essentially an NPC.

This is what I would call a soul. I don't believe they're immortal or anything, however.

Because our personality is defined by the brain. It's fully physical. I never said I believe souls have anything to do with personality.

I think they give some kind of meaning to the entire universe.

The universe mostly consists of particles that just exist. For inanimate things that do not perceive the flow of time, a Planck time is the same as the universe's entire lifetime. So without sentient observers, time would make no sense. The universe would instantly jump from its initial state to the final one, so it might as well not exist.

It's like in that philosophical question about a tree falling in the forest where no one hears the sound, but instead of the sound it's about time and therefore all existence. Sorry for bad English, I hope I made myself clear.

Tried to edit the post but for some reason it didn't work.

I feel like the question was poorly worded (English is my second language). By soul I meant a part of consciousness that makes us more than mere collections of atoms, not necessarily an immortal entity capable of afterlife/reincarnation.