Final answer:
The 'var' keyword in certain programming languages allows for type inference, where the compiler or interpreter determines the data type of a variable based on the initial value provided during declaration.
Step-by-step explanation:
If you're initializing a variable when it's defined, the var keyword in some programming languages (such as JavaScript) will determine the data type to use based on the initialization value. This is known as type inference. For example, if you assign a number to a variable using var, the language will automatically infer that the variable should be of a numeric type.
In other languages, such as C# or Java, the var keyword can also be used in a similar context, but it's relatively more recent addition than in dynamically typed languages. It allows the programmer to declare a local variable without explicitly stating its type, which the compiler infers from the value it is initialized with.