[I'm using the American spelling - luster. 'Lustre' is the British spelling.
It means a soft shine - the kind you get from satin. It can also mean the shine of highly polished metal.
"The official guards must shine their armor to a high luster."
It also means glory or magnificence of some great achievement.
"The luster of his award was still with him."
"The celebrity added luster to the party."