Improved a comment, fixed a typo

Author: Sergio0694

Microsoft.Toolkit.HighPerformance/Enumerables/SpanEnumerable{T}.cs

@@ -78,12 +78,12 @@ public readonly Item Current
                 ref T r0 = ref MemoryMarshal.GetReference(this.span);
                 ref T ri = ref Unsafe.Add(ref r0, this.index);
 
-                // On .NET Standard 2.1 we can save 4 bytes by piggybacking
-                // the current index in the length of the wrapped span.
-                // We're going to use the first item as the target reference,
-                // and the length as a host for the current original offset.
-                // This is not possible on .NET Standard 2.1 as we lack
-                // the API to create spans from arbitrary references.
+                // On .NET Standard 2.1 and .NET Core (or on any target that offers runtime
+                // support for the Span<T> types), we can save 4 bytes by piggybacking the
+                // current index in the length of the wrapped span. We're going to use the
+                // first item as the target reference, and the length as a host for the
+                // current original offset. This is not possible on eg. .NET Standard 2.0,
+                // as we lack the API to create Span<T>-s from arbitrary references.
                 return new Item(ref ri, this.index);
 #else
                 return new Item(this.span, this.index);