SOQL for loops

As we can read in the documentation:

SOQL for loops retrieve all sObjects, using efficient chunking with calls to the query and queryMore methods of SOAP API. Developers can avoid the limit on heap size by using a SOQL for loop to process query results that return multiple records.

It’s worth mentioning that the approach can increase the total heap size.

List<Account> accounts = [SELECT Id, Name FROM Account];

for (Account acc : accounts) {
    // ...
}

for (Account acc : [SELECT Id, Name FROM Account]) {
    // ...
}