What is the connection between Kiddush and the meal?

The Shulhan Aruch (O.H. 273:1), based on the Gemara (Pesahim 101a), rules that Kiddush is invalid unless it is recited in the place where the meal is eaten. The Rashbam (ibid.) deduces the Gemara’s ruling from the verse (Yeshayahu 58:13) “Vekarata LaShabbat Oneg” (lit. “and you shall call the Shabbat a delight”); in the place of calling the Shabbat, that is, Kiddush, you should have delight, that is, the meal. 

The Rashbam could be understood to mean that Kiddush has to be followed by a meal, or that any important meal must be preceded by Kiddush. One implication of the latter understanding would be that even Seuda Shelishit must start off with Kiddush. Although the Rambam (Shabbat 30:9) writes that it is proper to recite Kiddush for Seuda Shelishit, the custom is to only do so for the first two meals of Shabbat. 

The Shulhan Aruch goes on to state that the meal should be eaten in the same location as Kiddush. If one recites Kiddush in one part of a room and eats in a different part of the room, it is considered valid. Even if one changes rooms but those rooms are under the same roof, it is likewise valid. As such, Rabbi Ben Zion Abba Shaul (Or Lezion, vol. II, ch. 12, § 16) rules that if one recites or hears Kiddush in one apartment, one may eat the meal in another apartment, so long as they are in the same building. Nevertheless, Kiddush is invalid if recited in one house or building and the meal is eaten in another. 

The Kaf HaHaim (K.H, O.H., 273:58) quotes the opinion of Rav Nissim Gaon, who writes that if one may hear Kiddush in one place and have in mind to eat the meal elsewhere. Rabbi Ovadia Yosef (Halichot Olam, vol. III, pg. 2) says that, although the Shulchan Aruch implies that one may only have in mind to eat in another place when it is still under the same roof, in a situation in which one has no choice, one may rely on the opinion of Rav Nissim Gaon ex post facto. 

Summary:  Kiddush is only valid if followed by a meal. Kiddush must be recited in the same place as where the meal is eaten, which at the very least, is under the same roof.