I'm going to cover three subjects here:
- What does "kosher" mean?
- What is a kosher wine? What's a "Mevushal" wine?
- How can I tell if a wine is kosher?
What does the word "kosher" mean?
The word "kosher" means "fit." Kosher food is "fit to eat" because it passes certain technical requirements. Kosher food is often certified by rabbinical authorities, but it is not "blessed" by them.
What is a kosher wine? What's a "Mevushal" wine?
Wine has special rules and regulations that are unlike any other kosher food. With an important exception, kosher wines must be created, bottled, opened, handled, and poured only by Jews. If a non-Jew handles the wine — e.g., pours a cup of wine, or passes the bottle — the wine becomes not kosher.
There is an exception. If the wine is heated to near boiling, the wine can subsequently be handled by non-Jews — heating the wine affects the taste, as you might imagine. Wines that have been heated in this fashion are called "mevushal," and are so marked somewhere on the bottle (a few bottle have these notes only in Hebrew). Sometimes the abbreviation "Mev." is used. Almost invariably wines served at catered celebrations (e.g., a wedding) are "mevushal," since both Jews and non-Jews can be present or handle the wine.
You may want to look at this list of mevushal wines.
Of course, there can be other problems from time to time with wine; for example, the (thankfully infrequent) practice of adding ox blood to wine. Wines that are certified kosher will not have blood addded!
How can I tell if a wine is kosher?
Here on my wine rack in my office I've got a bottle of wine with the word "kosher" on it. But anyone can put "kosher" on a bottle of wine; the word is meaningless without testimony as to who put the word on the bottle. Since I don't know who — if anyone — certified the wine, I have yet to drink it.
How do I know who certified a bottle of wine? The bottle will be labeled with a trademarked symbol of an organization that certifies food as kosher.
Reliable kosher certification comes from many different organizations in all corners of the world. Much of the wine in the US is certified by either the OU or the OK. The OU's trademark is the letter O with the letter U inside; their web site is here. The OK logo is, similarly, the letter O with the letter K inside; their web site is here.
There are many other reliable certification organizations; for example, any bottle of wine marked "certified by the Chief Rabbinate" of a city in Israel is generally acceptable to most people in the Jewish community. Unfortunately, not all organizations are acceptable to all individuals, as might be imagined in a religious community which has no central authority (or, rather, many competing central authorities). The OU and OK are predominant in any case.
As I noted just above, a non-Jew may not open, pour, or handle an open bottle of wine. A non-Jew may give a Jew a sealed bottle of kosher wine. However, if that wine is not mevushal, the receipient would find it difficult to share the wine with the giver. Therefore, any kosher wine is perfectly acceptable as present; but as a host gift for a dinner invitation, a mevushal wine is a wise choice.
Again, to find mevushal wines, use the Guided Search or this list of mevushal wines.
