What are the drivers for short term/long term bond yields (how do they fluctuate? Through the purchases and selling of bonds?)

What are the drivers for short term/long term bond yields (how do they fluctuate? Through the purchases and selling of bonds?)

I ask this from the context of the inverted yield curve. How exactly does the short-term yield surpass the long term yield? I'm assuming the selling of bonds would create selling pressure to lower the asset values and then increase the yield (as they are inverted). I'm trying to understand the logic behind why the inverted yield curve would suggest a recession.