Insert

Account acc = new Account(Name = 'Riverbend Farms');
insert acc;

System.debug(acc.Id); // now populated — e.g. 001XX000003DHP0YAO

1. Account acc = new Account(Name = 'Riverbend Farms'); — before insert, acc.Id is null.
2. insert acc; — assigns the Id automatically the instant the insert succeeds.
3. (blank line)
4. System.debug(acc.Id); — now populated — this is exactly the 18-character Id format from Module 18.

List<Account> newAccounts = new List<Account>{
    new Account(Name = 'Riverbend Farms'),
    new Account(Name = 'Northwind Traders')
};

insert newAccounts;

for (Account acc : newAccounts) {
    System.debug(acc.Id);
}

1. List<Account> newAccounts = new List<Account>{ — a list of records to create.
2. new Account(Name = 'Riverbend Farms'), — the first, not yet saved.
3. new Account(Name = 'Northwind Traders') — the second, not yet saved.
4. }; — closes the list literal.
5. (blank line)
6. insert newAccounts; — a single DML statement covering every record in the list — this is exactly the bulkification instinct from Module 7's "Loops and Governor Limits" lesson.
7. (blank line)
8. for (Account acc : newAccounts) { — loops over the now-saved records.
9. System.debug(acc.Id); — each one now has a real, permanent Id.
10. } — closes the loop.

try {
    Account acc = new Account(); // no Name — Name is required on Account
    insert acc;
} catch (DmlException e) {
    System.debug('Insert failed: ' + e.getMessage());
}

1. try { — wraps the risky insert.
2. Account acc = new Account(); — no Name — Name is required on Account.
3. insert acc; — a record that violates a required-field or validation rule throws a DmlException here.
4. } catch (DmlException e) { — exactly Module 13's try/catch pattern, now catching a database-level failure instead of a runtime language error.
5. System.debug('Insert failed: ' + e.getMessage()); — handles it instead of crashing.
6. } — closes the catch.