Suppose four friends need to agree on pizza toppings. Depending on what culture they are from, they might follow several different procedures:

Everyone looks around, trying to catch each other's eyes, read body language, and guess who has the strongest preference for a particular kind of pizza toppings. Nobody wants to be the first to state their pizza preference if someone else has a stronger preference, since once somebody actually asks "Is it okay if we get mushrooms?" it would be very unkind to say no. Eventually, somebody says "How about Hawaiian pizza?" and everyone nods, even the person who doesn't want Hawaiian pizza, since it would be selfish to override someone else's preferences. The person who was first to ask loses a point.
After 4 seconds of waiting, someone says, "I like Hawaiian pizza. Anyone have a problem with that?" Someone else says, "I don't eat meat, is mushrooms and green peppers okay?" and then people nod.
One person says, "I'd like Hawaiian to be an option" and another person says "Plain cheese" and another says "Mushrooms and green peppers". Then everyone states how much they want each of those types of pizza on a scale from 0 to 10. Then, once everyone knows everyone else's preferences, it's hopefully obvious which pizza to order.

We could call the first type of system Guess Culture. In a Guess culture, it's considered rude, or costs face, to refuse a direct request. This means that if you ask somebody for the wrong thing - like "Can I have a cookie?", when they actually want all their cookies - they have to give it to you, and may be silently angry and resentful. This in turn means that you have to Guess whether the request is welcome before asking for anything. No one in Guess Culture can ever take the last slice of pizza. (You would think that a similar argument would then make it impossible to take the second-to-last slice, but Guess Culture pretends that other people are allowed to do what they want even though they're not actually allowed to do what they want. So you can take the second-to-last slice because anyone else who wants a slice is theoretically allowed to take the last slice, even though in practice they aren't.)

In the rarer Ask Culture, it's understood that people who don't want to meet a request will just say "no", with no harm done, thus enabling people to ask for things even if the request isn't welcome. E.g., "It's totally okay if you say no, but could I have one of those cookies?" Even with the disclaimer, this sentence won't work in a Guess Culture because the requestee is not allowed to just say no, regardless of what disclaimers were attached. There must be a common cultural understanding that you really truly are allowed to say no, before someone can ask if they can have a cookie without already being sure they're allowed to have it.

Tell Culture is a more extreme version of Ask Culture, in which someone might say, "Are you feeling not very attached to those cookies? I have a 3 out of 10 desire to know how they taste", trying to convey all the relevant info about their own mental state that could be helpful in making a decision, and the other person might reply, "I'm not super attached to these cookies but I think I'd feel 5 out of 10 bad about giving them up" and so the cookies are kept.

Obviously, you cannot just ask someone whether it's okay to use Ask Culture or Tell Culture rules in conversation with them. If they're from a Guess Culture, they won't be able to reply "No", even if they would actually be very offended.

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Good short article from The Atlantic