I believe true love is something that you are willing to sacrifice everything and anything for, including friends, family, your own life, etc.
But even true love is a result of neuronal connections and synapses. This fact shouldn't undermind the power of true love though. Everything we experience is the result of chemical reactions, when you boil down to the most fundamentals.
How do you know if you've found true love? Well, if you did, you won't even question it at all. If there is any doubt, you haven't attain it.