See initial public offering. When a company reaches a certain stage in its growth, it may decide to issue stock, or go public, with an initial public offering (IPO). The goal may be to raise capital, to provide liquidity for the existing shareholders, or a number of other reasons.
Sherbet (often pronounced sherbert in American English) is a frozen dessert made from iced sweetened fruit juice or puree. Sherbets usually have more ingredients, such as milk, egg whites, or gelatin, than sorbets, which are generally made from iced fruit puree and other ingredients.
Sorbet has no milk. Sherbet is somewhere between the two - it has milk and water. Gelato is Italian for ice cream. Calling ice cream gelato might mean you avoid some of the laws about fat and/or milk in ice cream (I'm not sure about that though - mostly it makes it sound better).