A woman lying in the grass in the park is wearing a red top and black capri pants and is barefoot.
A woman is lying in the grass.
" A woman is lying in the grass "   is another form of saying  "  A woman lying in the grass in the park " as grass is seen in the park.
Is lying in the grass is a paraphrase of lying in the grass.
A woman is lying in the grass is the same as a  woman lying in the grass.