What exactly is purchasing power parity (PPP)? I have some questions regarding what exactly PPP is. In my understanding, PPP is essentially the value that a currency can purchase within an area. For example, although the USA might have more money in the international area, the total amount of monetary value can purchase more goods in China due to the low price of living there. 

The problem I have with this is that it seems that value is subjective. For example, it might be cheaper to purchase labor in China than in the US however it is much more costly to purchase an iPhone there. How you decide which is more valuable? 

If what I am saying makes no sense at all, please explain what PPP is.
What you are describing is basically purchasing power. Purchasing Power Parity (PPP) claims that your purchasing power is the same across countries.

PPP states that, if say a pound of bread costs 4 US$, you can take that amount, exchange it to Chinese yuan, go to China and buy exactly the same amount of bread. (i.e. you have the same purchasing power in both countries)

3 factors play a role: the price (of bread) in the US, the price in China, and the Exchange rate. There is no subjective factor here.

Even though I don't fully understand what you mean by "purchasing labor", make sure that you compare goods, or baskets of goods, only (PPP does not say anything about wages or production costs).

And be sure to remember that PPP does not necessarily have to hold in reality.

Hope this helps!