--Sample Table
CREATE TABLE EMPLOYEE (
Empl_Id NUMBER(6),
First_Name  VARCHAR2(50),
Last_Name   VARCHAR2(50),
DOB         DATE,
Dept_Id     NUMBER(3))
TABLESPACE HR_Section;

CREATE TABLE Department(
Dept_Id NUMBER(3),
Dept_Name   VARCHAR2(50),
Empl_Number   NUMBER(2))
TABLESPACE HR_Section;

CREATE TABLE PayRoll
Empl_Id NUMBER(6),
Salary  NUMBER(6),
Tax     NUMBER(6),
Vacation NUMBER(2))
TABLESPACE HR_Section;

--BASIC INSERT
Syntax:
INSERT INTO [TableName] ([ColumnName])
VALUES ([Value]);

--INSERT SELECT
Syntax:
INSERT INTO [TableName] [SELECT];

--RECORD INSERT

INSERT INTO [TableName]
VALUES [RecordName];

Ex:
CREATE TABLE ItEMPLOYEE AS
SELECT Empl_Id, First_Name , Last_Name
FROM EMPLOYEE
WHERE Dept_Id  =1001;

DECLARE ItGuy  ItEMPLOYEE%ROWTYPE;

ItGuy.Empl_Id := 4521;
ItGuy.First_Name := 'LAMBERT';
ItGuy.Last_Name := 'JONES;

INSERT INTO ItEMPLOYEE
VALUES ItGuy;

--INSERT WHEN

--INSERT WITH CHECK OPTION

Using the WITH CHECK OPTION ensure that Oracle prohibits any changes to the row not matching the condition.

INSERT INTO ([SELECT] WITH CHECK OPTION)
VALUES ([Value]);
Ex:
INSERT INTO (SELECT deptno, dname, loc
FROM Department
WHERE Dept_Id=1001 WITH CHECK OPTION)
VALUES (1011, 'Development', 10);

--inserting Into SELECT

Syntax:
INSERT INTO ([SELECT]) VALUES ([Value]);

INSERT INTO (SELECT Empl_Id ,Salary ,Tax ,Vacation FROM PayRoll) VALUES (14521, 60000, 750, 32 ) ;

--INSERT Create Table

Syntax:
CREATE TABLE [TableName] AS [SELECT];

--INSERT With Returning

Syntax:
INSERT INTO [TableName] ([ColumnsName])
VALUES [Values]
RETURNING [ColumnName]
INTO [VariableName];

Ex:
EMPLOYEEIdSequence here is a Sequence for EMPLOYEE ids.

INSERT INTO EMPLOYEE (Empl_Id, First_Name , Last_Name)
  VALUES (EMPLOYEEIdSequence.NEXTVAL, 'Thomas', 'Dulley' )
  RETURNING Empl_Id
  INTO Return_val;