Comparing Apex Triggers & .NET Triggers
As in any other programming language, a trigger in Force.com Apex listens for a specific condition, such as a new record being inserted in a field, and invokes one or more associated Actions (e.g. send email) in response.
In a most common design pattern – you will create a trigger to listen for an event (e.g. record update) – and then call an Apex class from the trigger; the Apex class contains the logic for the action which needs to be taken.
In many ways – apart from the syntactical and other differences between Apex and C# – the concept of triggers is very similar in both.
What are the common events in Force.com? Inserts or updates or deletes of a record in a field are typical “events” – since on Force.com you primarily create database driven applications.