Last lesson you wrote your fields on paper — today they become real variables. A variable is a named place for a value: a labelled box the program puts data into and takes data out of.

Go gives you three ways to create one:

• Full form — var title string = "Dune". Everything spelled out: the word var, a name, a type, a value. Use it when you want the type in black and white, or when declaring without a value.
• Short form — pages := 380. Go infers the type from the value (380 → int). This is the default form inside functions — you will see it the most.
• Constant — const appName = "Book list". A value that never changes while the program runs. Assigning to it again does not even compile.

When to pick which:

Situation	Form
A normal variable inside a function	:=
Declare now, assign later	var
Fixed for the program's lifetime	const

Tip. := only works inside functions. At file level (next to import) only var and const are allowed — you will see this in the very next step.