What is Trigger in Salesforce?

Apex triggers are the primary mechanism for executing custom server-side logic in response to data changes. A trigger defines a timing context (before or after), one or more DML events, and the sObject it monitors. Before triggers are used to validate or modify field values before the record is saved to the database, while after triggers are used when you need access to system-set fields like Id or to perform operations on related records.

Best practice dictates a one-trigger-per-object pattern, where the trigger itself contains minimal logic and delegates to a handler class. This keeps code testable, avoids order-of-execution conflicts when multiple triggers exist on the same object, and simplifies bulkification, the practice of writing code that efficiently handles batches of up to 200 records per DML operation. Trigger context variables (Trigger.new, Trigger.old, Trigger.newMap, and Trigger.oldMap) provide access to the records being processed. Clientell AI can generate trigger-handler scaffolds from plain-language descriptions and ensure they follow Salesforce's bulkification and single-trigger patterns.