Where are Pentatonics used in jazz?

Because they have the jazz "vibe" or "feel".

Sorry misread the question.
Pentatonics are a particular type of scale much like a blues scale.
They do give a particular type of feel to the progressions which can be termed as jazzy or bluesy.

There are more in depth explanations which I am sure someone on here will help with. And are more qualified than me.
As a singer I can sing them, but not too good on the explaining.

There are many situations where pentatonic scales can be used. They can be used in many different chords.

Also, there are many different pentatonic scales besides the traditional major and minor pentatonic scales. Get yourself a scale book to learn how to use all of them, and the best chords to play them over.

The various Pentatonic scales are used to good effect all over jazz tunes.

The Minor pentatonic scale is where the blues scale is derived from (By adding an extra note)

Many great jazz players spent a great deal of time soloing using pentatonic scales intermingled with blues, myxolydian scales etc. Too many to name really.

Listen to Candy Dulfer on alto saxophone, she uses them all the time in her soloing.

They are used on dominant seventh chords for example you can play a c-major pentatonic on a C-Dominant Chord, which is also the same thing as an a-minor pentatonic scale.

On minor seventh chords, there are about six possible pentatonic scales for each chord for example, on a C-minor seventh chord you can play a c-minor pentatonic, d-minor pentatonic, e-flat major pentatonic, f-major pentatonic, g-minor pentatonic and b-flat major pentatonic.

On major seventh chords, there are five possible pentatonic scales. For example, on a C-major seventh chord, you can play a c-major pentatonic, d-major pentatonic(add an F-sharp or #4 on major seventh chords), e-minor pentatonic, g-major pentatonic and a-minor pentatonic.

On minor major seventh chords, there are two possible pentatonic scales. For example, on a C-minor major chord, you can play a d-minor pentatonic and f-major pentatonic scale.

When you play the blues, you can play minor and major pentatonic scales on their respective dominant seventh chords. For example in a blues piece in B-flat major, you can play a B-flat major or minor pentatonic scale on the B-flat dominant seventh chord and you can play the B-flat minor pentatonic scale on the other chords in the piece such as the E-flat dominant and F dominant chords which would also be played in the B-flat major blues piece.

There are even other kinds of pentatonic scales that I did not cover.

You do not always have to play pentatonic scales on these chords, it is up to your own personal flavor and tastes.

i like man of gold's answer, exept when you are playing an f, make it F#, for a Cmaj 7 chord
c maj pent; dMAJOR pent; e min pent, g maj pent, a min pent,