It is not specified for only one person but the served meal (salad etc.) is for everybody at the table.
For example, cheese served at the middle of the table.

This phrase means the item is not an individual plate but is served for everybody at the table. The best translation I can think of is “served for all the guests”.

This applies to meals that are cooked for several persons.

The example optimal control gave in his answer is perfect: when you order a fondue, it is common that you have to order it for at least two people, with the cheese being put between all those who take part in it.

Edit: I actually thought of one case when the meal is served for all the guests. When you negotiate with a restaurant for large tables, it is common to establish a restricted menu in order to make things easier/faster. In such cases, this mention may make some sense.

Although this phrase could describe the type of service employed in “family-style” meals (where everyone starts with an empty plate and serves themselves from communal serving bowls/platters), it is more often found in conjunction with “Menus dégustations.” or “Tasting Menus” and is used, not really as a description of the service (for the service is usually elaborate and sequential [à la russe]), but as more of a “warning” that all guests (by table if multiple ‘Menus dégustations’ are offered, but for the entire restaurant if there’s only one offered) are required to “participate” in the “dining experience” by ordering (and paying for) the same “tasting menu.”

The menu for L’Ermitage uses the phrase (with “de la table” added) with its two “Menus dégustations,” and translates it as “menu is only served for the whole table,” but when used in connection with ‘menus dégustations’, I think that non-literal equivalents found on many English “Tasting Menus” capture better the important “warning” aspect of the phrase, such as

Tasting menus require the participation of the entire table

found at the bottom of Luce’s tasting menu.

Or the slightly more literal:

Please note that this menu is to be taken for the entire table

found at the bottom, along with the “per person” price reminder, of Forbury’s sample “Menu dégustation.”

While forcing all the guests (at a table in a restaurant) to order the same thing (“participate”) is contrary to the notion of “free choice” generally associated with restaurant dining, it’s argued that “they’re [not] trying to be difficult—it’s because they want to deliver the best possible experience,” according to Juni’s Commandment 3 of tasting menus.