HTTP Status Codes are the 3 digit integers which contain in server response. There is a meaning for each number. Response Header of each API response contains the HTTP Status Code. The first digit of the Status-Code defines the class of response. HTTP Status Codes are grouped into five categories based upon the first number. 

Following are the SET of status codes with its meaning:

• 1xx: Informational-It means the request has been received and the process is continuing. 
• 2xx: Success-It means the action was successfully received, understood, and ACCEPTED. 
• 3xx: Redirection-It means further action must be taken in order to complete the request. 
• 4xx: Client Error-It means the request contains INCORRECT syntax or cannot be fulfilled 
• 5xx: Server Error-It means the server failed to fulfill an apparently valid request. 

Some of the commonly seen HTTP Status Codes are: 200 (Request is Ok), 201 (Created), 202 (Accepted), 204 (No Content), 301 (Moved Permanently), 400 (Bad Request), 401 (Unauthorized), 403 (Forbidden), 404 (Not Found), 500 (Internal Server Error), 502 (Bad Gateway), 503 (Service Unavailable) etc.