Confused about lots...??

[Forex Trader]

If I fund an account with $10,000 what does “one lot” equate to?

I’ve read that regardless of your initial deposit, one lot always equals 100,000 US. (unless it’s a mini lot).

So, if I only put in $10,000 - and trade one lot, where does the extra 90K come from? Is the bank giving me a loan?

And what if the trade goes south, and I loose all 100K, am I liable for the 90K I borrowed from the bank?

Sorry for the newbie question - but I haven't seen it answered in the sources I checked.

Thanks!