im sure there is a thread like that, but the search engine doesn't always work well.

The "S" on a lipo battery refers to the number of cells. Why it isn't called a 2C I do not know. A 2s (2 cells) lipo has a nominal voltage of 7.4v. A 3s (3cells) lipo has a voltage of 11.1v. These are nominal voltage...when fully charged they read higher and when drained read lower.

Your model is setup to use a pair of 2s lipos in series (series doubles the voltage, so the speed control (ESC) gets 14.8 volts) The other term you will see that is similar is running to batteries in parallel....this doubles the runtime, not the voltage.

MAH....basically equals runtime. The more, the better. For most applications, 5000mah packs work very well.

"C" rating. you will see on some packs both a constant and a burst "C" rating. This is basically how many amps the battery can put out quickly. 30c rated packs work well for 1/10 and 1/8 models. Nothing wrong with using a higher C rated pack and typically the higher that rating the higher the quality of the cells.

The red plugs on the redcat are not standard. They are pretty good at handling the voltage/amps that most models need.
There is no standard plug. Some use Deans (or T style copies of the deans) some use traxxas plugs, some use EC3 and cheap stuff still uses Tamiya (or molex) white plugs. Those Tamiya plugs will melt if used with a lipo...they cant handle the amps.
There is nothing wrong with changing to deans or traxxas plugs....but there is nothing wrong with staying with the stock plugs either. And you can find batteries sold with different plugs on them...so use whatever you like.

The 3 wired white plug...that is called the balance plug. Id imagine your stock charger uses this to charge (most slow charges do)
Lipo cells work different then old nimh batteries. If you charge them without that white plug hooked up to your charger, the cells will over time become unbalanced...more voltage in one than the other. This becomes a problem as the speed control reads the total voltage of your batteries and cuts power to the motor when it reads a certain voltage level. Lipo batteries cannot be fully drained like old nimh packs. So if cells become unbalanced, the esc may read 6.2v, but one cell has 3.5 and the other has dropped below 3v (you don't want a cell to drop below 2.9v as this risks damaging it)

while it is not nessasary , I balance charge my lipos every time. It takes an extra 10 minutes or so to balance charge verses just charging them.

If you google something like RC Lipo Battery info then you should come up with some threads specifically on lipo batteries. They have a few extra rules than the old nimh packs, but their performance is SOOOO much better that it is worth it to read up.