Context is very important.
"Natural Law" can mean many different things depending on the context...from philosophy to ethics to scientific principles etc.
Generally, it refers to universal principles/rights/values...what should be inherent to everyone...things that should apply to everyone:
For example, the right for all human beings to live, to be happy, to be free, to have human dignity, autonomy (This should not just apply to just men or just women, just the rich or just the poor..those in the US or those in Africa...it should apply to everyone...and it should ALWAYS be applied regardless of the culture/government).