Each cell in a lipo has a nominal 3.7 volts. The amperage will vary from manufacturer to manufacturer.
Soooooooooo, a 4s2p 4,400 mah lipo battery breaks down as follows:
4 cells in series (providing 14.4 volts). (Each individual cell in this example, has 3.7 nominal volts AND 2,200 mah). The volts determine the power.
and
2 sets of the 4 cells in parallel. Each SERIES set of 4 cells would have 2,200 mah. The cells in parallel are to increase the amperage of the battery pack. The amps in a pack determine how long the pack will provide power. More amps, more flying time.
Now I will throw the curve ball.....When a lipo cell is FULLY charged it typically reads 4.1 - 4.3 volts PER CELL.
When calculating battery size for you plane use the NOMINAL voltage. For instance, 14.4 volts would be a 4S battery.
Hope this answers some questions