The second type is the vague invitation.
A vague invitation is generally the simplest form of tentative invitation. This kind of invitation usually comes up casually as if the conversation has just led to it—it is not particularly definite or sincere. For example, when you are talking about food and getting into specific details, you can say: “Oh, I heard that restaurant is pretty good; we should go try it sometime.” Or “I’m not bad at cooking; I’ll let you taste my cooking sometime.” Such invitations are usually tied to the ongoing topic. By integrating the invitation into the current conversation, it comes across very naturally. The probability of being rejected in this situation is very low, as it carries little sense of demand and does not feel forced.