I am a neophyte when it comes to high end audio. I was reading an older forum on LPCM. I saw a review on the Sony STR-DG820. The reviewer mentioned the Sony by virtue of having LPCM has True HD? Is this true? If it is true then what is the big deal with True HD?

I am trying to buy an average A/V receiver, but want it to be relevant in 5 years? What do you look for?
Thanks