What is the difference between lazy and eager loading?

Lazy loading defers the initialization of an object until the first time it is accessed. Eager loading initializes the object immediately when the main object containing the reference is loaded.

Differences:

Characteristic	Lazy Loading	Eager Loading
Loading Time	At first use	When loading the main object
Load	Distributed over time	All at once at the start
Memory	Saves memory initially	May require more memory immediately
Performance	Better when working with part of data	Can be faster if all data is needed immediately

Example in Hibernate:

// Lazy loading
@Entity
public class Order {
    @OneToMany(fetch = FetchType.LAZY)
    private List<Item> items;
}

// Eager loading
@Entity
public class Order {
    @OneToMany(fetch = FetchType.EAGER)
    private List<Item> items;
}