let’s  take a look at the simple definition of variables in SSIS

Variables store values which can be used  to update tasks in control flow , data flow and in event handlers,   dynamically during the run time of the package

Types of Variables

1) System variables (system defined)

2) User defined Variables

How they are accessed(scope)  :  system variables can be accessed from any task(if it allows) in the package and these can only be read

User Defined Variables :    are created by the users  and data types include    string, int16, int32, int64, double,  dbnull, object, single,  Boolean, char, Uint32, Uint64, datetime, sbyte

how they accessed in the package is kind of different from system defined variables and now we can start using the word called scope

if a variable is created in data flow  (scope)  it can not be accessed from control flow

so lets consider different scopes here

Package level :  a variable created with out highlighting any of the task in  control flow

Task level : a variable created with highlighting any of the tasks in control flow

Data flow :  variable  created in data flow by selecting or not selecting any tasks are transformations in data flow

Important : variables are case sensitive

a variable as Var1 is not same as var1