The ternary operator is a compact way to write simple if/else statements. It has three parts: a condition, a result if the condition is true, and a result if it is false. Here’s the basic syntax:

condition ? expressionIfTrue : expressionIfFalse;

Here’s an example dealing with weather temperatures in Celsius:

const weather = temperature > 25 ? 'sunny' : 'cool';
 
console.log(`It's a ${weather} day!`);

If temperature is greater than 25, the code above logs It's a sunny day!. If temperature is ever less than 25, it logs It's a cool day!.

So, which should you use between an if statement and a ternary? Use a ternary while dealing with a single condition or single expressions, or when you want a compact syntax for simple logic. Use if/else statements when you’re dealing with complex conditions and multiple statements, as things become unreadable if you nest ternaries.