YTM v.s. market interest in bond valuation

hi there,

i am always get confused about "yield" (i guess it equals to YTM) and "market interest"...

YTM is decided by par value, coupon rate, maturity and "market interest rate", rite? it is actually the 1/Y of the cash flow generated by the bond.

So, the only variable factor here is the interest rate, which is decided by the market level? and YTM and interest are positive correlated?

In this case, when we talking about interest rate risk, actually we are talking about the risk from whole market's volatility?

BTW, who will calculate the trading price of a bond? the exchange? And each exchange choose interest rate they feel correct? is that possible that different bonds use different interest rate estimation?