system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: how can money lose value?

So ive always sort of understood the idea of inflation and that the dollar loses value, but ive never understood how? Like the more money in the market, the lesser the value, but correct me if im wrong in saying that money is an idea used to unify selling and spending in a quanitative way so people can fairly access what they’re purchasing/selling and its worth? So why not just make the amount of the currency whatever you want? It just seems like currency is an arbitrary number rather than something of actual significance and ive never understood that?
gpt
Let's say your family household is the nation's economy.  Dad's making middle class income, you get $5 for doing chores, but buying a new $1,200 GameBox is expensive for the family. 

Then Dad gets a raise.  He's providing more value to his company, and in turn they're paying him 10x more! Now, the family can buy the new $1,200 GameBox without thinking about it.  That's **good inflation** because while money is worth a little less to the family it's not because the dollars are worth less outside the home's economy.  There's simply more money to go around, and anyone can spend more of it outside the household (read: foreign economy). 
  
In another universe, Dad got his pay cut for being bad at his job.  Now you're only getting $1 for the same chores because that's all the family can afford.  You have to do 4x as many chores just to squeeze an extra $1 out of Mom.  That's **Bad Deflation**, because the dollar's value outside the economy hasn't changed, but within the household the scarcity of dollars has made them worth more.  

Turns out, Dad works for the US Mint printing dollar bills.  He feels really bad about cutting your pay for the same work, so he prints himself off an extra $5000 at work and brings it home.  Now the family can buy the $1200 GameBox because money isn't an issue, but they aren't providing any extra value to the global economy.  That's **Bad Inflation**, because if Dad keeps doing it, GameBox will have to up their price to $12,000 because the dollar isn't worth as many chores as it used to be due to all the extra dollars going around. 

**Good Deflation** occurs when the Mint fires dad and starts collecting all those extra bills Dad printed.  This brings the GameBox price back down to $1,200 and prevents all the other global economies from riding a crazy roller coaster while they try to balance themselves again.  Another example of Good Deflation would be when GameBox needs to stimulate their own economy and lowers the price to $500, so you don't need to do as much work to buy what you need because the dollars in your house are now worth more to GameBox's economy. 

When trying to understand the Macro Economics of a nation that can print it's own bills, you'll go crazy trying to make all the numbers add up.  It's best to imagine that every dollar given to the US Treasury/Federal Government (taxes, etc) is immediately taken out back and burned, removing it from the economy (Deflation). Then imagine every dollar spent by the Federal Government (roads, army, etc) as one that is freshly printed (Inflation). 

This is why the US Congress doesn't have to actually balance their budget to zero expenses vs income.  They literally print an infinite amount of new bills to pay for every program, and balance it with an estimate of what will be burned out back each year in taxes/fines/literal fires. Very smart people analyze every program and advise Congress how much a new program will inflate or deflate the dollar.  

So, something like the COVID Stimulus prints a shitload of money, inflating the dollar, but giving us a short-term boost that helps people not starve.  The theory is that we'll recoup it with taxes or stimulate some new industry that directly competes (and wins) with another country like China or Mexico, forcing them to lower their prices.