Balance a pencil on your finger and you will quickly learn that the pencil behaves as if its entire mass were concentrated at the center of the pencil, the center of mass. The center of mass between any number of particles lies at an average point between those particles. If you apply pressure at that central point, the entire structure of the pencil is lifted uniformly and is balanced.
This is also true on a planetary scale. As the Earth and the Moon move around each other, there exists a center of mass between them. Since the Earth is 81.6 times more massive than the Moon, the Earth is closer to the center of mass, which is actually located below Earth's crust. Earth's tides follow this imaginary center of mass, not the movement of the Moon across the sky. The particles that comprise objects like pencils, or systems like the Earth-Moon, interact with space-time to create a center of mass, the effect of all the particles warping space-time.
Now let's try a thought experiment. Imagine a sphere, whose central point cannot be lifted, because it is hollow and contains no structural elements. Like all objects, the sphere also behaves as if its mass were concentrated at an imaginary center. The gravitational field induces this effect. Eliminate the mass of the sphere and replace it with a force that resists the intrusion of space-time, a bubble in space-time. And just like a bubble in water resists the ocean surrounding it, this imaginary sphere pushes back on the ocean of space-time. And importantly, this imaginary space-time bubble would have a gravitational mass proportioned by its distortion on space-time.
If you were to accumulate thousands of your imaginary space-time bubbles in close proximity; they would be forced tightly together by the resisting pressure of space-time. If you were to try to lift them, you only need to lift the center bubble, because the weight of all the bubbles would be concentrated there, the center of mass. In this thought experiment your imagination recreated mass.
Mass is a bubble in space-time, created by the pressure of space-time around itself. We use particle accelerators to break mass apart into smaller bubbles, but as we do the ocean of space-time surrounds those fragments and we literary create new and smaller fragments. We even give our favorite fragments names like atoms, protons, leptons and bosons. But we can never find a basic particle, because mass is constructed from the torque of space-time around itself. And as Einstein first told us, if we break the torque that space-time holds on mass, we release energy (E=Mc^^2).
So the next time you hold a pencil in your hand, balance it from your finger and feel that center of mass take notice. The pencil itself feels weightless, only the center appears affected by gravity, because the effect of all the other mass has been canceled out and the weight you feel on your finger is concentrated into that center. You are holding a virtual space-time bubble on your finger, but you can split that pencil into smaller fragments for infinity and never find it, because it isn't real, only the effect is real. Likewise, there is no basic particle, only the basic principle that mass is a bubble in space-time.