is the sim free and unlocked version of iphone X the same thing

Sim-Free - You pay upfront the entire price of the phone, and then buy a contract from whichever carrier you wish to connect through.

Unlocked - In theory you're able to buy a contract from whichever carrier you wish to connect through, however "unlocked" implies that at some time in the past the phone was carrier locked - Sold on a contract tied to a particular carrier, with the initial 'up front' price heavily subsidised by that carrier (they make up the full price on the monthly charge). While the phone is carrier locked you can only use that carriers SIMs. The official way to unlock a phone is to get the carrier to do it for you - there would likely be a charge for this.

Whether Sim-Free is available for you will depend on your territory. I'd suggest going to the Apple website, ensuring your correct country is listed bottom right of the page, then clicking through as if you are selecting an iPhone for purchase. The various options for your country will come clear.