What are context variables in Salesforce Triggers?

Hii Sanjana,

Context variables, as the name implies, refers to the fact that what the context of the trigger fire is . These are basically the implicit variables that that allow developers to access run time context. Some of the examples of context variables are isInsert, isUpdate, isDelete etc.

Hi,

All triggers define implicit variables that allow developers to access run-time context. These variables are contained in the System.Trigger class.

Variable

isExecuting
Returns true if the current context for the Apex code is a trigger, not a Visualforce page, a Web service, or an executeanonymous() API call.
isInsert
Returns true if this trigger was fired due to an insert operation, from the Salesforce user interface, Apex, or the API.
isUpdate
Returns true if this trigger was fired due to an update operation, from the Salesforce user interface, Apex, or the API.
isDelete
Returns true if this trigger was fired due to a delete operation, from the Salesforce user interface, Apex, or the API.
isBefore
Returns true if this trigger was fired before any record was saved.
isAfter
Returns true if this trigger was fired after all records were saved.
isUndelete
Returns true if this trigger was fired after a record is recovered from the Recycle Bin (that is, after an undelete operation from the Salesforce user interface, Apex, or the API.)
new
Returns a list of the new versions of the sObject records.This sObject list is only available in insert, update, and undelete triggers, and the records can only be modified in before triggers.
newMap
A map of IDs to the new versions of the sObject records.This map is only available in before update, after insert, after update, and after undeletetriggers.
old
Returns a list of the old versions of the sObject records.This sObject list is only available in update and delete triggers.
oldMap
A map of IDs to the old versions of the sObject records.This map is only available in update and delete triggers.
size
The total number of records in a trigger invocation, both old and new.

Hope this helps!