Learn Hardcore Arabic (Modern Standard): الإنقاذ مهم اليوم.

ق in إنقاذ is a deep q sound, not an English k.
ذ sounds like th in this.
مهم is pronounced roughly muhimm.
In normal pause at the end of a sentence, final case vowels are often not pronounced.

Why is there no word for is in the sentence?

Because Arabic usually does not use a present-tense verb meaning is/am/are in simple sentences like this.

So:

This is called a nominal sentence in Arabic.
The idea of is is understood automatically.

If you wanted a past or future meaning, then Arabic would use a verb, such as كان for was.

What kind of sentence is this grammatically?

It is a nominal sentence: a sentence that begins with a noun.

Its parts are:

So the structure is basically:

[subject] + [description/comment] + [time expression]