This study investigates the electronic and magnetic excitations in La₃Ni₂O₇, a high-temperature superconductor under pressure. Using X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS), the researchers identified that Ni 3dₓ²⁻ᵧ², Ni 3d_z², and ligand oxygen 2p orbitals dominate the low-energy physics with a small charge-transfer energy. The study reveals well-defined optical-like magnetic excitations that soften into quasi-static spin-density-wave ordering, indicating strong electronic correlations and rich magnetic properties. An effective Heisenberg spin model was used to extract a much stronger inter-layer effective magnetic superexchange than intra-layer ones, proposing two viable magnetic structures. The findings emphasize that the Ni 3d_z² orbital bonding within the bilayer induces novel electronic and magnetic excitations, setting the stage for further exploration of La₃Ni₂O₇ superconductor. La₃Ni₂O₇, a bilayer nickelate, exhibits high-temperature superconductivity at 80 K under pressure. Unlike cuprate superconductors, La₃Ni₂O₇ hosts Ni ions with mixed valences and unpaired electrons in both 3dₓ²⁻ᵧ² and 3d_z² orbitals. The molecular bonding between the two inter-layer Ni 3d_z² orbitals through the apical O p_z orbital is proposed as a critical ingredient for the low-energy electronic structure. The orbital character governing the electronic properties of unconventional superconductors is essential for understanding the underlying pairing mechanism. In cuprates, the small charge-transfer energy and strong hybridization between Cu 3dₓ²⁻ᵧ² and O 2p orbitals lead to the formation of the strongly correlated Zhang-Rice singlet band, which serves as the foundation for describing the electronic properties including the superconducting pairing interaction with dₓ²⁻ᵧ² symmetry. In contrast, iron-based superconductors feature relatively weaker correlation and multiple 3d bands near the Fermi surface. La₃Ni₂O₇ appears to be a sibling of iron-based superconductors due to its multi-orbital nature and bad metallicity in the undoped parental phase. However, perovskite nickelates are also known to exhibit strong electronic correlation and small charge-transfer energy, resembling cuprates. Theories vary in their opinions on which orbitals are most relevant for the electronic properties, especially the superconductivity, in La₃Ni₂O₇. The antiferromagnetic (AFM) superexchange interaction is accepted as another important ingredient of unconventional superconductors. Upon the doping of charge carriers, the long-range AFM-ordered parental phase evolves into one with short-range AFM spin fluctuations, which may mediate the superconducting pairing. In a sizable part of the phase diagram, the interplayThis study investigates the electronic and magnetic excitations in La₃Ni₂O₇, a high-temperature superconductor under pressure. Using X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS), the researchers identified that Ni 3dₓ²⁻ᵧ², Ni 3d_z², and ligand oxygen 2p orbitals dominate the low-energy physics with a small charge-transfer energy. The study reveals well-defined optical-like magnetic excitations that soften into quasi-static spin-density-wave ordering, indicating strong electronic correlations and rich magnetic properties. An effective Heisenberg spin model was used to extract a much stronger inter-layer effective magnetic superexchange than intra-layer ones, proposing two viable magnetic structures. The findings emphasize that the Ni 3d_z² orbital bonding within the bilayer induces novel electronic and magnetic excitations, setting the stage for further exploration of La₃Ni₂O₇ superconductor. La₃Ni₂O₇, a bilayer nickelate, exhibits high-temperature superconductivity at 80 K under pressure. Unlike cuprate superconductors, La₃Ni₂O₇ hosts Ni ions with mixed valences and unpaired electrons in both 3dₓ²⁻ᵧ² and 3d_z² orbitals. The molecular bonding between the two inter-layer Ni 3d_z² orbitals through the apical O p_z orbital is proposed as a critical ingredient for the low-energy electronic structure. The orbital character governing the electronic properties of unconventional superconductors is essential for understanding the underlying pairing mechanism. In cuprates, the small charge-transfer energy and strong hybridization between Cu 3dₓ²⁻ᵧ² and O 2p orbitals lead to the formation of the strongly correlated Zhang-Rice singlet band, which serves as the foundation for describing the electronic properties including the superconducting pairing interaction with dₓ²⁻ᵧ² symmetry. In contrast, iron-based superconductors feature relatively weaker correlation and multiple 3d bands near the Fermi surface. La₃Ni₂O₇ appears to be a sibling of iron-based superconductors due to its multi-orbital nature and bad metallicity in the undoped parental phase. However, perovskite nickelates are also known to exhibit strong electronic correlation and small charge-transfer energy, resembling cuprates. Theories vary in their opinions on which orbitals are most relevant for the electronic properties, especially the superconductivity, in La₃Ni₂O₇. The antiferromagnetic (AFM) superexchange interaction is accepted as another important ingredient of unconventional superconductors. Upon the doping of charge carriers, the long-range AFM-ordered parental phase evolves into one with short-range AFM spin fluctuations, which may mediate the superconducting pairing. In a sizable part of the phase diagram, the interplay