There are a lot of websites already using Stellar's built-in decentralized exchange (Stronghold, Stellarterm etc). What will be released shortly is an official exchange/front-end by the Stellar Foundation that utilizes the SDEX and will soon also support FIAT currency so it's basically a fully fledged decentralized exchange with fiat trading pairs.

i have here many question in my post today but i will try to give some answer also ... if any one can guide us in this regards that what is the stellar foundation going to launch? i think it is great news for stellar holder, lover, and it is best time to buy stellar,, hope i am correct here.

• How are they able to support fiat currency?
  Anchors operating on the network, they serve as a fiat gateway to make deposits and withdrawals.

• Who runs the Anchors? The guys that create the anchors, it’s your task to choose who you trust. If Bank of America launches an USD anchor then you’ll trust it.

There are crypto anchors: BTC, ETH, LTC, XRP... Fiat anchors: EURT, PHP, WSD (USD anchor), CNY, JPY... Soon carbon credits. And so on... You can read about anchors here: https://www.stellar.org/developers/guides/anchor/

Yeah, they are not really focusing on banks at the moment, more remittance companies. And IBM is totally onto Central banks digital currencies.

• It’s not only possible, it’s a built in feature. This is also very good for companies that want to trade assets like stocks or real estate on the chain.

This is one of the central value propositions of the stellar network.

A bank or other entity acts as a “trusted anchor.” Think something like Coinbase. You can send the anchor USD, for example, and they’d issue you “USD token” on the stellar Blockchain. They can also be trusted to receive “USD token” and send you actual USD.

You can then trade the usd token for bitcoin, XLM, or whatever you choose. In most instances, the anchor immediately and automatically swaps the USD you deposit for Bitcoin, XLM, etc, to avoid the auditability issues surrounding coins like Tether. However, with a transparent auditing scheme, you could actually trade fiat, gold, or even stocks on Stellar.

Note that, unlike ETH dexes like IDAX, the stellar DEX is nearly instant and nearly feeless. You can even perform trades right out of your ledger or other wallet. It’s AWESOME.

• What does atomic pathfinding mean?
  So the atomic bit means either it all happens or it all fails - you won't be left stranded in an intermediary currency, right?

And the pathfinding bit is routing you through a series of currencies to give you the best conversion rate - sound about right?

Also, is this SDEX something that merchants could use? So you might pay them in ETH and they choose to get paid in fiat or whatever? Or am I barking up the wrong tree on this one?

• Atomic swaps means that swaps between multiple currencies are guaranteed.. as in if you are going from USD->BTC->XLM->EURO then you are certain to be able to make the whole transaction, not just a part of it; either the entire swap goes through or none of it will. Pathfinding finds the cheapest exchange rate between two assets. Suppose it was USD and EURO again...instead of the above, it might be cheaper to do USD->LTC->XLM->EURO. And since stellar supports the tokenization of assets, the stellar network could do something like USD->LTC->Bananas in Colombia->goats in Sengal->seashells in south Florida->XLM->EURO if it was the cheapest atomic swap available. All automatically at that.

Stellar won before the game even got going.