Analogy: Think of a cache line as a secret you know.
- Modified (M): Only I know the secret, AND I've changed it. The memory doesn't know the new version yet. I must write it back eventually.
- Owned (O): I know the secret, others also know it, but I am the "Headmaster". If someone else asks for it, I am responsible for giving it to them.
- Exclusive (E): Only I know the secret, and it's the exact same as what's written in the memory. I can change it whenever I want without asking anyone.
- Shared (S): I know the secret, others also know it. I cannot change it without asking the Interconnect first.
- Invalid (I): I don't know the secret, or the version I have is too old (Garbage).