Motion to Recommit (MTR) in House vote

I've been following U.S. politics for a while. I'm seriously confused with the MTR process. It seems like when a bill is ready to be voted on in the House, one member from the minority party can change the content of the bill, and everyone will vote on it. I don't get it. So the Democrats can propose a bill for a $12 billion rail system for example. A Republican can propose an MTR to change the content of the bill to instead fund a $3 billion wall...and everyone will vote on it? If it passes, the bill is dead and won't be voted on again.<br><br>I don't understand this rule one bit. Could someone explain it to me pls.