A group of people are standing before a food truck and buying something.
Some people are standing before a food truck and buying a taco.
The first sentence claims that there is a food truck but doesn't say what kind of food. The second sentence clearly states that the food truck is where you can buy a taco.
exists e1 e2 x1 x2 x3 x4 x5 x6 x7.(Theme(e2,x7) & Actor(e2,x5) & v_buy(e2) & n_thing(x7) & of(x5,x6) & n_people(x6) & n_group(x5) & before(e1,x3) & n_truck(x3) & of(x3,x4) & n_food(x4) & Actor(e1,x1) & v_stand(e1) & of(x1,x2) & n_people(x2) & n_group(x1))
exists e1 e2 x1 x2 x3 x4 x5.(Theme(e2,x5) & Actor(e2,x4) & v_buy(e2) & n_taco(x5) & n_people(x4) & before(e1,x2) & n_truck(x2) & of(x2,x3) & n_food(x3) & Actor(e1,x1) & v_stand(e1) & n_people(x1))