It looks like some type of open brain coral...It is an LPS, maybe either Wellsophyllia or Trachyphillia. Why did you purchase it if you don't know what it is or what it ate?
You need to check all of your water peramiters, temp, salinity, what type of lighting do you have? Report this information back here when you figure it out.
They are photosynthetic creatures which also feed on meaty items like shrimp. What else do you feed your tank?