Hoisting means the JS engine registers variable and function declarations before running any code line by line.

• var declarations are hoisted and initialized to undefined
• let/const are hoisted but stay uninitialized (temporal dead zone) until their line runs
• Function declarations are fully hoisted, including their body
• Function expressions and arrow functions are NOT hoisted the same way

console.log(x); // undefined (not an error)
var x = 5;

console.log(y); // ReferenceError: Cannot access 'y' before initialization
let y = 5;

greet(); // Works! Function declarations hoist fully
function greet() { console.log('hi'); }