Answer:   Governor limits are considered as the biggest challenge for the Salesforce developers. Salesforce came with a concept called Governor limits to ensure there should be no single clients monopolizing the shared resources. There are various governor limits while considering Salesforce namely

com Platform Apex Limits
Size-specific Apex limits
Email Limits
Per-Transaction Apex Limits
Static Apex Limits
Miscellaneous Apex Limits
Push Notification Limits