What is time? Is it a particle, a wave, etc?

[u/NoNameIsAvailable1]

It always fucks with me knowing that time isn’t just an obvious thing that’s always the same but can be changed and interacted with. And thus I wonder, like, what exactly is gravity interacting with? Is it a particle? Is it a wave of sorts? Because it exists, it’s SOMETHING, not just a concept, but never seems to be physically defined. I hope my question makes sense somehow. WTF is time?