Triggers in Salesforce | Triggers in Apex | Trigger Context Variables | How to write triggers?

What is an apex trigger or apex triggers in Salesforce?
How does apex trigger work?
How to write Apex triggers in Salesforce Developer Console?
What are the different DML operations on which we can write Apex triggers?
Which are the different Trigger Context variables in Apex triggers?

KEY MOMENTS -

What are the triggers in Apex - 00:27
Creating an apex trigger from Developer console - 01:01
Events and Triggers (DML operations) - 02:28
Example of a typical apex trigger code - 02:42
Trigger Context Variables - isBefore, isInsert, etc. - 03:39
Testing or executing a trigger in Developer console - 04:12
Trigger Context Variables - new, old, newMap, oldMap - 05:57
Trigger Context Variables example - 06:57