Likpo deals with 3 diff voltages - the cell minimum voltage, a nominal voltage and the cell maximum voltage. Lipos cells are all alike in this regard. If you overdischarge a cell below ~3volts (cell minimuim), you can damage the cell (it will swell or puff). Likewise, if your overcharge a cell above the cell maximum of 4.2v, it can swell and or vent, again damaging the cell. The nominal cell voltage of 3.7v is basically used for comparison - usually when lipo voltage is mentioned, its on the basis of the nominal voltage.

Lipo batteries are assembled using multiple cells wired in series. Wiring in series makes the voltage add, so two cells wired in series (2S, the 2 is the number of cells is series) would be 3.7v + 3.7v = 7.4v nominal. This 2S lipo coming off the charger fully charged would read 2 x 4.2v = 8.4v and should not be discharged below 2 x 3v =~6v. I use approximate cause some lipo cells are more sensitive to low voltage than others. I personally use 3.2v/cell as my cutoff.

A lipo capable charger prevents overcharging - its built in to stop at 4.2v/cell as soon as you tell charge you're charging a lipo. The low voltage protection is provided usually by your esc - most modern opnes have some kind of low voltage cutoff (LVC) builtin. Some ar eprogrammable as to voltage ans some are programmed for specific voltages already. There are also add-on type devices for escs that do not have an lvc.

Run time is dependent on battery capacity - mah (milliamp-hours) of the battery. This is like a gas tank. Bigger number, longer it will run. The "C" is the lipo discharge rating - what amperage the lipo can produce. Its simply calculated from mah and C rating as capacity(mah)/1000 x C = amps discharged. So for the 5000mah 35C pack you mentioned, it can discharge 35 x 5000/1000 = 175amps. This provides a basis to compare lipo capabilities from brand to brand and influences price as well.

There are a lot of chargers out there, are you looking for an AC/DC charger?