Having good eating habits is very important.这里的have和eat为什么用动名词

Having good eating habits（动名词是主语）
is very important.
Having good eating（动名词是定语） habits
译文：
拥有良好的饮食习惯是很重要的.也就是说，动名词是主语还是定语。having和eating都是主语吗？也就是说，动名词是主语还是定语。having和eating都是主语吗？不都是主语呢。Having good eating habits（having...动名词是主语） Having good eating（eating动名词是定语） habits