Well I can give you an answer but you will probably not be satisfied by it. First let’s disregard the “Cat” and consciousness; the “Cat” because it will only confuse and consciousness because it is not needed.
An observation occurs when the Unitary Evolution (and the [deterministic] equations that make it up) must be abandoned in favor of State Vector Reduction) and the [non-deterministic] equations that make it up). This does not require consciousness; a photon detector can trigger collapse of the wave function.
In QM there is really nothing “physical” to describe the interaction -- it is a mathematical construct. And just so you see that giving a “physical” explanation doesn’t add any meaningful details: a physical explanation would be -- when a quantum of information is exchanged between the observer and the observed state vector reduction occurs. Some scientists have tried to define this as at least one graviton in quantity. The only trouble is that we don’t know what a graviton is, what “quantity” it would be or if there really is such a thing as a graviton. Some have tried to relate the difference to the possibility of reversal (which is possible in Unitary Evolution) and non-reversibility (which is not possible in Vector State Reduction). Which is of no help -- to me at least.
I am afraid if you want a more classical physics type answer you will never find it. Quantum Mechanics requires a change in your world view. It can never be fitted to the classical world view no matter how much mental gymnastics you expend.
In some sense some might relate it to a woman; you may be able to appreciate it but never to really understand it.