"The number before the S is the number of cells in series to give your pack voltage.
The number before the P is the number of parallel batteries in your pack.
So a 3s1p pack is 3 cells in series, 1 set of these series cells in parallel.
A 3s2p pack is 2 sets of 3 cells in series.
Some packs, to get the C rating up and therefore a higher discharge amp rating, will use mutiple strings of series cells in parallel to boost the current and C rating of the pack.
You can do the same thing by paralleling independent packs together (of the same rating). 2 qty 8C packs in parallel give you 16C."