"The cheese is in the refrigerator."
Translation:El queso está en el refrigerador.
The two words refer to the same appliance, but the usage is regional.
Technically nevera comes from nieve, and is thus more analogous to our word icebox, which in the old days simply stored ice.
Whereas the refrigerador like our refrigerator "recools" the inside using magical thermodynamics.
I had this thought when doing the exercise. I THINK that 'este' mainly means 'this' and 'that' etc. and as janisjordan began to explain 'esta' is indeed the 3rd person singular. But I am a relative beginner to Spanish and am willing to be corrected by people far more adept at this than I.
In order to be sure exactly why it marked you wrong, you would need to either copy and paste or take a screenshot of your full answer so we can see what you wrote.
If it turns out you spelled everything correctly and your grammar was good, it's possible the volunteer course contributors simply forgot to add options with "nevera" to this sentence. Each prompt has its own separate answer database which the volunteer course contributors curate manually. Oversights happen. In that case, simply flag it after it marks you wrong and before you move on and report "My answer should be accepted". If enough people make that same report, they will investigate the matter.