Apply suggestions from code review

Co-authored-by: Benjie <[email protected]>

src/pages/learn/schema.mdx

@@ -165,7 +165,7 @@ This means that wherever we use the type `Episode` in our schema, we expect it t
 
 ## Type modifiers
 
-Types are assumed to be nullable and singular by default in GraphQL. However, when you use these named types in a schema (or in [query variable declarations](/learn/queries/#variables)) you can apply additional _type modifiers_ that will affect the validation of those values.
+Types are assumed to be nullable and singular by default in GraphQL. However, when you use these named types in a schema (or in [query variable declarations](/learn/queries/#variables)) you can apply additional _type modifiers_ that will affect the meaning of those values.
 
 As we saw with the Object type example above, GraphQL supports two type modifiers—the [List](https://spec.graphql.org/October2021/#sec-List) and [Non-Null](https://spec.graphql.org/October2021/#sec-List) types—and they can be used individually or in combination with each other.
 
@@ -179,7 +179,7 @@ type Character {
 }
 ```
 
-Here, we're using a `String` type and marking it as a Non-Null type by adding an exclamation mark (`!`) after the type name. This means that our server always expects to return a non-null value for this field, and if it receives a null value, then that will trigger a GraphQL execution error, letting the client know that something has gone wrong.
+Here, we're using a `String` type and marking it as a Non-Null type by adding an exclamation mark (`!`) after the type name. This means that our server always expects to return a non-null value for this field, and if the resolver produces a null value, then that will trigger a GraphQL execution error, letting the client know that something has gone wrong.
 
 As we saw in an example above, the Non-Null type modifier can also be used when defining arguments for a field, which will cause the GraphQL server to return a validation error if a null value is passed as that argument: