Understanding a Trigger in Salesforce.com

Hi again:
This will be the first of many lessons on Triggers. But before I start writing triggers in salesforce.com, I need to explain triggers and how they work. One needs to understand before anything. So lets start.

1. What is a Trigger?

"A Trigger is a block of Apex Code that executes in response to a particular type of change in a record's data." from the Force.com Developer Guide Page 336

• What does the above definition mean in simple English. Basically a trigger is an event that fires off when a record is changed.
  
• by changed I mean, you can:
• Update a Record - Updating an existing record.
• Insert Record - Inserting a new record like a new Account or Contact.
• Delete Record - before the record deletes make sure everything is valid.
• These three Actions we call (Update, Insert, Delete) are the main functions of a trigger. Basically which one will use a trigger for.
• Also one can use a trigger as a controller combine with Visualforce or calling a web service API.
• People have asked the question "How can I override the Save button in Force.com" Plain and simple way is to write a trigger. Why or How?
• Simple, when you create or update a record the only way your new information weather you added information to an existing record or changed it or you added a new record, one would have to click SAVE to place the information into the database.
• By clicking Save if you have a trigger on that Object then you can fire it off, thus overriding the save button. It will save and do the commands you wrote in the trigger itself.
• Also, triggers must be written in Sandbox and then deploy to server via eclipse tool.
• It must pass the standard requirement of 75% in sandbox before deploying into production.
  

I hope this cleared many questions about understanding a trigger. My next post will be on writing a trigger and implementing it.
Thanks
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