Make small edits to FastX overview (MystenLabs#524)

* Make small edits to FastX overview

Corrected plural IDs and moved an "only" for precision

* Update overview.md

doc/overview.md

@@ -4,6 +4,6 @@ FastX is a distributed ledger that stores a collection of programmable *objects*
 
 The ledger is updated via a *transaction* sent by a particular address. A transaction can create, destroy, and write objects, as well as transfer them to other addresses.
 
-Structurally, a transaction contains a set of input object ID's and a pointer to a Move code object that already exists in the ledger. Executing a transaction produces updates to the input objects and (if applicable) a set of freshly created objects along with their owners.
+Structurally, a transaction contains a set of input object references and a pointer to a Move code object that already exists in the ledger. Executing a transaction produces updates to the input objects and (if applicable) a set of freshly created objects along with their owners.
 
-A transaction whose sender is address *A* can only accept objects owned by *A*, with one exception: a transaction can read from immutable objects regardless of their owner.
+A transaction whose sender is address *A* can accept objects owned only by *A* with one exception: a transaction can read from immutable objects regardless of their owner.