Level of Development, as embodies primarily in Computer Aided Design (CAD) assets. LOD 500 refers to the most detailed CAD possible - the elite of all CAD - with come caveats as in the link below.
Points: LOD 500 is as-built-detail - which may remove some detail of LOD 400 and retain only what's important to customer for purposes of facility management (FM)
LOD (Level of Development) vs Level of Detail - the latter refers only to geometry. The former includes interface between parts.