Make the point more clear (#1601)

Author: sourishkrout

src/content/learn/Learn-Schema.md

@@ -297,7 +297,7 @@ Learn more about this in the [inline fragments](/learn/queries/#inline-fragments
 
 ### Union types
 
-Union types are very similar to interfaces, but they don't get too specify about any common fields between the types.
+Union types share similarities with interfaces; however, they lack the ability to define any shared fields among the constituent types.
 
 ```graphql
 union SearchResult = Human | Droid | Starship