Buffer information overload, help!

[Nocaster Cat]

I understand what buffers do but I'm having difficulty figuring out why there are so many. Is it just different ways of skinning a cat? Any insight would be greatly appreciated. And yes, I did use the SEARCH function but that's what lead to the confusion. 

[Gus]

First you need to define what you mean by Buffer.

I think of a buffer as a close to gain of one circuit that has a input resistance that you want and output resistance and drive that you want.

A buffer can be built many ways, emitter follower(EF) circuit, bootstrapped EF, opamp circuit, Tube circuit, Jfet circuit , MOSFET circuit, maybe even an IGBT circuit.  Can be one active device or more than one active device of different types.

How I pick
what supply voltage and current is available?
what input resistance is desired?
what output resistance is desired?
will the buffer drive a capacitive load like a long cable?
what parts do I have? If an unused 1/2 of an opamp maybe use that
what part(s) I want to build with.

If you want more than about a gain of one I use the term gain stage, again you need to select your input and output resistance and the other things listed above.

[AudioEcstasy]

Essentially a buffer just changes impedance, usually high input to low output in order to drive long cable runs without tone suck, HF loss, etc. There are many ways to utilize them and a lot of great info on the net about them!

[earthtonesaudio]

There are many features a buffer can have, but only one they MUST have, and that is isolation.  Buffers isolate the input from the output or vice versa.  Hence the name.

[Gus]

 If I understand  Nocaster Cat correctly.  Why so many different ways of building one?

I believe the answer might be, because you can build them different ways people will build them different ways.