The ternary operator is technically that: an operator. But, it's also kind of an if/else substitute. It's also kind of a ?? alternative, depending on the situation. The ternary expression is used to conditionally assign a value. It's called ternary because it has three portions: the condition, the value if the condition is true, and the value if the condition is false.

String alert = isReturningCustomer ? 'Welcome back to our site!' : 'Welcome, please sign up.';

In the above example isReturningCustomer is a boolean. If it is true, the variable called alert will be assigned the value "Welcome back to our site!". Otherwise, alert will be assigned the value "Welcome, please sign up.".