That transition is flush and without any intermediate material... a finely crafted detail by the contractors (Rough Workshop). They did a great job of setting the tile first within a 1/16" of where the height of the flooring would be, then tuned the wood to match that height. It's a grout joint, which can crack over time if things move, but stays cleaner than caulk.

Let me know if you have more questions or you can also inquire with the contractor directly (their Houzz page is here: http://www.houzz.com/pro/roughworkshop/rough-workshop).