A Vital Point is an important shape point for both players. Vital points are usually urgent. (Though not all urgent moves are concerned with shape) Vital points are key points in either the local, or, perhaps less commonly, the global context.
White is a classic example of a vital point
A point that maximizes the effectiveness of the stones. Similar to tesuji or best move, but with a different nuance. A tesuji is a strong move within the context of a sequence of moves, but if you occupy a vital point, it's hard for the opponent to gain a good result no matter where he plays. Of course, the two are not completely distinct.
is a vital point for shape.
From Jowa, Powerful Fighter (Gohwan Jowa) by Takagi Shoichi, p. 60.
Below are examples from TournamentGo1992, page 152 (left column) and page 154 (right column). They are taken from the game record and commentary from the game Otake Hideo (White) vs Kobayashi Koichi (Black), 30 September and 1 October 1992, the third game of the 17th Meijin Title. 
Takemiya is quoted as saying "White should play...at in Dia. 3. After , he can take up position with . I think that the latter is the vital point of the whole board."
 Question: Is this the same as the "crucial point"?
Bill: Crucial point is not go jargon. So who knows, but probably not, or the author would have said, vital point, instead.
OneWeirdDude: I've always held it was the "point at which a formation lives or dies" - or something like that.
David: How does one determine what the vital point is? How many moves ahead do you have to be looking in order to know where the vital point is?
Uberdude: The vital point often doesn't come from reading, but jumps out at you from your intuition of shape (e.g. Example 1). This is developed by playing games and doing tesuji and life and death problems.
David: Thanks! For a beginner, this is a pretty overwhelming concept.
axd: "crucial"? "vital"? and there's "critical" too?
- if these all mean the same, I'm about to replace that term in Killable Eyeshapes Introductory with "vital" - I think that term covers all.
- so unless someone correctly defines the different terms, I am about to edit away these other terms (or at least move them out of the main text stream). let's minimise confusing and redundant terms, shall we?
Bob McGuigan: All these terms are translations of the Japanese 急所, (kyuusho). In the context of life-and-death "vital point" seems the most appropriate translation. In fact "vital point" is the definition listed first in Japanese-English dictionaries. However, the term is also used to describe the key point for shape, and "vital point" does not seem so good in this usage when life-and-death is not an issue. "Key point" is also a listed meaning in dictionaries and this might be more appropriate than "vital point" in the shape context. The Japanese word is part of general usage and the go meanings are the same as in general use. So I don't see it as a special technical word. The ordinary English meanings of "crucial", "vital", and "critical" work just fine in the Go context. In fact there are ordinary English words used in Go for which the Go meaning is much more obscure. For example "big", as in "Urgent moves before big moves". I hope people don't forget all their ordinary language use when discussing go. "Vital, "crucial", "critical", and "key" seem close to synonymous.