Eager Loading: Eager Loading helps you to load all your needed entities at once. i.e. related objects (child objects) are loaded automatically with its parent object.
When to use:
Lazy Loading: In case of lazy loading, related objects (child objects) are not loaded automatically with its parent object until they are requested. By default LINQ supports lazy loading.
When to use:
NOTE: Entity Framework supports three ways to load related data - eager loading, lazy loading and explicit loading.