A magnetic field is a fundamental force field that is associated with the behavior of electrically charged particles in motion. It is not made up of particles itself, but rather it exerts a force on charged particles and can be described mathematically using vector fields.
In classical physics, magnetic fields are explained by the concept of electromagnetic fields. These fields arise due to the motion of charged particles, such as electrons in an electric current. According to classical electromagnetism, a changing electric field gives rise to a magnetic field, and a changing magnetic field induces an electric field. These two fields are intertwined and propagate through space as electromagnetic waves.
In the framework of classical physics, magnetic fields and electric fields are both manifestations of the electromagnetic force, and they can be described by Maxwell's equations.
In the context of general relativity and the warping of spacetime, gravity is indeed different from electromagnetism. Gravity is described by the curvature of spacetime caused by mass and energy. In the case of gravity, the presence of mass and energy warps the fabric of spacetime, and objects move along the curved paths dictated by this curvature.
While the electromagnetic field can have an effect on the curvature of spacetime in the presence of very intense fields, such as near black holes, on a fundamental level, the electromagnetic field is distinct from the curvature of spacetime associated with gravity.
In summary, a magnetic field is not made up of particles itself, but it arises from the behavior of charged particles in motion. It is described by an electromagnetic field and its interactions with charged particles can be explained using classical electromagnetism. The relationship between magnetic fields and the curvature of spacetime is indirect, and the electromagnetic field is distinct from the curvature of spacetime associated with gravity.