for (variable : [soql_query]) { code_block }

for (variable_list : [soql_query]) { code_block }

//The same previous example using For SOQL Loop
List<apex_invoice__c> PaidInvoiceNumberList = new List<apex_invoice__c>();//initializing the custom object records list to store the Invoice Records
List<string> InvoiceNumberList = new List<string>();//List to store the Invoice Number of Paid invoices
for (APEX_Invoice__c objInvoice: [SELECT Id,Name, APEX_Status__c FROM APEX_Invoice__c  WHERE CreatedDate = today]) {//this loop will iterate and will process the each record returned by the Query
	if (objInvoice.APEX_Status__c == 'Paid') {//Condition to check the current record in context values
		System.debug('Value of Current Record on which Loop is iterating is '+objInvoice);//current record on which loop is iterating
		InvoiceNumberList.add(objInvoice.Name);//if Status value is paid then it will the invoice number into List of String
	}
}
System.debug('Value of InvoiceNumberList with Invoice Name :'+InvoiceNumberList);