Your First SOSL Search

List<List<sObject>> searchResults = [
    FIND 'Riverbend Farms' IN ALL FIELDS
    RETURNING Account(Id, Name)
];

List<Account> matchingAccounts = searchResults[0];
System.debug(matchingAccounts.size());

FIND 'Riverbend Farms' names the search text; IN ALL FIELDS means search every searchable text field; RETURNING Account(Id, Name) names which fields to return for matching Account records.

List<List<sObject>> searchResults = [
    FIND 'Riverbend Farms' IN ALL FIELDS
    RETURNING Account(Id, Name), Contact(Id, LastName)
];

List<Account> accounts = searchResults[0]; // matches from Account
List<Contact> contacts = searchResults[1]; // matches from Contact

This is exactly Module 16's "Nested Collections" pattern applied to search results: the outer List has one entry per object named in RETURNING, in the same order they were listed, and each inner List<sObject> holds that object type's matches — searchResults[0] for the first object named, searchResults[1] for the second, and so on.

List<Account> matchingAccounts = (List<Account>) searchResults[0];

Depending on how the result is used, you may need to cast the inner List<sObject> to its specific type — this is Module 18's sObject polymorphism concept (a specific type can be cast back down from the generic base type) showing up directly in a real SOSL result.