var Keyword

Defining a variable as var enables to assign any data type value. var is implicit data type declaration.

var str = "hello";

var num = 10;

var is statically defined: Compiler checks assigned value to var and create data type accordingly at the declaration (compile time)
var num = 10; //compiler creates num as int at this declaration
var str = "hello"; //compiler creates str as string at this declaration

var is strongly typed: At declaration compiler create appropriate data type by checking assigned value so from next statement of declaration variable behaves like strongly typed variable
str++ //error because its now string
num++ //allowed because its now int
intellisense showing all prop/methods of string for 'str'

object & dynamic can also be used but these both resolved at run time. They are dynamically defined and not strongly typed.