update tutorial

Author: iliailmer

docs/src/tutorials/parameter_identifiability.md

@@ -1,6 +1,6 @@
 # Parameter Identifiability in ODE Models
 
-Using ordinary differential equations for modeling real-world processes is commonplace and the challenge of parameter identifiability is one of the key design challenges. In this tutorial, we will show how to use `StructuralIdentifiability.jl` with `ModelingToolkit.jl` to assess parameter identifiability.
+Using ordinary differential equations for modeling real-world processes is commonplace and the problem of parameter identifiability is one of the key design challenges. We say that a parameter is identifiable if we can recover its value from experimental data. When we describe the parameter without actual data at hand is _structurally_ identifiable. In this tutorial, we will show how to use `StructuralIdentifiability.jl` with `ModelingToolkit.jl` to assess parameter identifiability.
 
 We will start with determining local identifiability, where a parameter is known up to finitely many values, and then proceed to determining global identifiability properties, that is, which parameters can be identified uniquely.