Booster what does it mean??

[SuperMiguel]

I keep seeing post like this:

In most cases, you're going to be better off with two RAF chains:
A > B > C
A > D > E

And a booster on A.

If you're brand new, without a booster, you'd level five toons on ABCDE... in such a way that the first composition of five includes a booster on A, for the later sets.
You'd want the booster to hit 85th or higher, at which point you can boost through the 80th level dungeons quite easily.

If you have at least one existing booster already, you can boost immediately.

Because of having two RAF chains... and gaining the ability to give 39 levels, if you level a set of toons from 1st to 80th...
And with two RAF chains going...
You boost a set of toons on BCDE, with A.
Then level a toon on A to 2nd level (and almost to third), then apply granted levels from both chains... and that is a full toon on A.

And you get the cascade granted levels.
For every four toons on BC and DE, C gives two 80s to B (actually boosts two toons from 2nd and almost third), and that lets B give an extra full toon to A in addition to the normal granted toons... same deal with D in the DE chain.

If you boost/level four toons on BCDE, with A...
You get:
A x6 Granted Toons
B x4 Boosted Toons + 2x Granted Toons
C x4 Boosted Toons
D x4 Boosted Toons + 2x Granted Toons
E x4 Boosted Toons

What do people mean by booster? i understand is a high lvl toon(85+), but what do i do with him? Group with the other low levels and do what?