Hi,
the reliability means how long does this chip works,
or due to leakage the life time of the chip. another
factor is under high power supply, does the chip or devices work well or not.
the burn in means test the device under low supply voltage, high temp. or put the device under critical condition to see the life time of the device
Statistically, most parts have short life time, or very long life time. If the parts passed the burn-in test, they will have long life time. Burn-in test is used to selected the qualified parts
Reliablity - It tells how good the chip can work into different factor of operation.
Etc- when the chip operated under different power supply,
temperature, interfaces and so on.
Quality - It tells how good the chip in terms of convincing the customers. Let say we are manufacturing about 100 unit, and out that about 95 unit works well. So, we say the chip is in good quality. Basically this quality is mainly checked at the end process of manufacturing.