Static vs Instance Members

Every field and method you've written so far — eventName, price, describe() — is an instance member. Each EventTicket object gets its own separate copy of eventName and price; that's why two tickets can have different prices at once.

public class EventTicket {
    public String eventName;
    public Decimal price;

    public static Integer ticketsCreated = 0;

    public EventTicket(String eventName, Decimal price) {
        this.eventName = eventName;
        this.price = price;
        ticketsCreated++;
    }
}

EventTicket t1 = new EventTicket('Conference', 1200);
EventTicket t2 = new EventTicket('Workshop', 400);

System.debug(EventTicket.ticketsCreated); // 2

1. public class EventTicket { — the blueprint.
2. public String eventName; — an instance field — one copy per object.
3. public Decimal price; — another instance field.
4. (blank line)
5. public static Integer ticketsCreated = 0; — static means there is only one copy of this field total, shared by every EventTicket object ever created — not one per ticket.
6. (blank line)
7. public EventTicket(String eventName, Decimal price) { — the constructor.
8. this.eventName = eventName; — sets this object's name.
9. this.price = price; — sets this object's price.
10. ticketsCreated++; — increments the shared counter every time any ticket is created.
11. } — closes the constructor.
12. } — closes the class.
13. (blank line)
14. EventTicket t1 = new EventTicket('Conference', 1200); — creates the first ticket, incrementing ticketsCreated to 1.
15. EventTicket t2 = new EventTicket('Workshop', 400); — creates a second, incrementing it to 2.
16. (blank line)
17. System.debug(EventTicket.ticketsCreated); — accessed through the class name, not through any specific object — logs 2.

public class TaxCalculator {
    public static Decimal applyVat(Decimal amount) {
        return amount * 1.15;
    }
}

Decimal total = TaxCalculator.applyVat(100); // 115, no "new" needed

1. public class TaxCalculator { — a class with no fields at all, just a calculation.
2. public static Decimal applyVat(Decimal amount) { — a static method belongs to the class itself, not to any object.
3. return amount * 1.15; — the calculation.
4. } — closes the method.
5. } — closes the class.
6. (blank line)
7. Decimal total = TaxCalculator.applyVat(100); — called directly on the class name, without ever creating a TaxCalculator object — fitting for a calculation that doesn't depend on any one object's specific data.