i just mean applying backpressure... on fixed it will transfer energy to the wheel and slow you down or make the bike travel backwards or break traction with the ground, on free it will just spin the freewheel bearing and do nothing.

the sides don't work at the same time you have to take the wheel off and turn it around so that the side you want to put the chain on is on the right side of the bike.
here's what it looks like put together

the freewheel is closer to you in the picture, the track cog is on the other side. if you were to put it on the bike with the side facing you on the chain, you'd have a freewheel singlespeed and could coast, if you turned it around and put it on the bike, the fixed gear would be on the chain and anything the wheel does the pedals do, so if the wheel's in motion you have to be pedaling.

here's one on the bike with the fixed side on the chain.

if you took that wheel off and flipped it, the freewheel could be used with the chain.