In plain words: Apex errors occur when your code encounters an unexpected situation—like reading an unassigned variable (Null Pointer), requesting a record that does not exist (Query Exception), violating validation rules (DML Exception), or hitting multi-tenant resource caps (Governor Limits). Salesforce Apex executes in a strongly typed, multi-tenant cloud runtime. While this architecture guarantees system security and shared resource availability, it also enforces strict execution rules. Encountering exceptions is part of everyday development, but understanding why they happen and how to resolve them defensively makes your code resilient, scalable, and production-ready.
Topic
Apex
Apex Development