A skateboarder is doing a trick in the air with his skateboard on a red ramp while people stand around looking.
He is performing skating tricks with onlookers on the side.
The second sentence just elaborates more on the skateboarder doing tricks in front of onlookers which in this case is synonym for the people standing around.
exists e1 p1 s1 x1 x2 x3 x4 x5.(n_skateboard(x4) & of(x4,x3) & n_male(x3) & n_air(x3) & exists e3 e2 x6.(around(e2,e3) & Actor(e3,x6) & v_look(e3) & Actor(e2,x6) & v_stand(e2) & n_people(x6)) & while(e1,p1) & with(e1,x4) & on(x4,x5) & n_ramp(x5) & a_red(s1) & Theme(s1,x5) & Theme(e1,x2) & Actor(e1,x1) & v_do(e1) & in(x2,x3) & n_trick(x2) & n_skateboarder(x1))
exists e1 e2 x1 x2 x3.(n_side(x3) & for(e1,e2) & with(e2,x1) & on(x1,x3) & n_onlooker(x1) & Theme(e2,x2) & Actor(e2,x1) & v_skate(e2) & n_trick(x2) & Actor(e1,x1) & v_perform(e1) & n_male(x1))