When the government of Argentina says they're going to peg the peso to the US dollar that means that if you come and give them a peso they will give you a US dollar in return. That's a 1 way peg.

A 2 way peg would mean you could get a peso for a dollar in the US and you could get a dollar for a peso in Argentina.

With cryptocurrencies a peg can't function this way since there isn't any authority, such as a national government, who can make such a commitment.

So what are we talking about when we say 2 way peg?

According to my understanding it means that if you send an amount of BTC, let's say amount X to a particular address A, this address is associated with a different cryptocurrency, ETH for instance ,on blockchain B.

Then having sent X of BTC to A you will have some amount of ETH proportional to X on blockchain B, until you decide to reverse the peg and have your BTC insead of ETH. Is that how it works?