Meaning of parameters A, B and C in Pymatgen Structure summary

Hello, this is my first time working with pymatgen. Viewing structures found through Materials Project I notice parameters A, B and C. What are they called. Thank you

Structure Summary
Lattice
    abc : 7.572005 8.501789489291358 10.65389274884265
 angles : 79.66596564696403 78.4046972827287 63.822206395350726
 volume : 599.7225777590837
      A : 7.572005 0.0 0.0
      B : 3.750633 7.629756 0.0
      C : 2.141407 1.076928 10.380753
    pbc : True True True
PeriodicSite: Lu (6.5359, 0.3987, 2.6253) [0.7834, 0.0166, 0.2529]
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