system
Given the following post, respond as if you're commenting on Reddit:
human
What exactly does a physicist mean when using the word Information?

I understand that the answer to this question is probably going to be fairly general, so allow me to provide some of the specific instances in which I have heard the term, in order to provide some context.

Information Theory
Is information destroyed when it moves beyond the event horizon of a black hole?
The quantum teleportation of information

Just to make this clear, I'm not looking for an explanation of those three greater concepts. They are there only to give those of you who are much more knowledgeable than I an easier time knowing what in the world I am actually asking.

Thanks in advance!
gpt
Information is just the ability to distinguish between two states. Consider an electron which has two possible spin states: spin up and spin down. It's possible to measure the spin of the electron. When you do, you will gain 1 bit of information. There are two possible spin orientations but we've reduced it down to 1. Great.

It turns out that information has some physical properties. Special relativity states the information cannot travel faster than light and the second law of thermodynamics states that we lose more information than we gain in every performed experiment.

Recently, it turns out that these concepts are critically important to studying computers (which are physical systems after all) and black holes.

The black hole information paradox is related to quantum mechanics. In quantum mechanics, every system evolves (changes) in a reversible way (information preserving). This is called unitarity. However, it seems like the action of a black hole is fundamentally irreversible. However, people disagreed with this and proposed mechanisms for black holes to store and emit information to resolve the paradox.