hint_normal triggers the reimport of a texture as a normal map when a texture is supplied using the inspector. This is done because normal maps only need the red and green channels to function (Godot reconstructs the blue channel in the shader). This makes it possible to use more better-looking and efficient RGTC compression for VRAM texture compression.
hint_albdo triggers the reimport of a texture to perform sRGB conversion. When using the GLES3 renderer, Godot performs rendering in linear space to allow for gamma-correct, HDR rendering.