Two things: 1.It means to either prime the siphon action on the tube so it can start. With homebrewing, this is easily accomplished with an autosiphon. 2. To give the yeast a small amount of sugar, usually dextrose, to rouse themselves produce enough CO2 after being bottled. Special care must be taken to use the right amount and to sanitize the bottles. Using too much will sugar will result in over pressurization of the bottle and lead to the bottles exploding. After 2-3 weeks, the sugar will complete be metabolized by the yeast into CO2, bring the contained beverage to a certain volume of CO2. This is not typically done with wines, unless it's a "sparkling wine". Note that if you do wish to carbonate a wine, you cannot use standard wine bottles as the corks are not designed to with stand the increased pressure. Instead, use beer bottles or a champagne corker.