A type rating is a certification issued by the country’s regulatory body (such as DGCA in India) that certifies that a pilot is fit to fly certain types of aircraft which requires additional training beyond the scope of the initial license and aircraft class training. What aircraft. In many countries pilots of certain aircraft do not require a type rating for each model, all or most such aircraft being covered by one class rating instead. 

Once you have graduated from a flight school with CPL along with multi-engine and instrument rating, you are eligible to become a First Officer. You may need to get type rated on a certain type of aircraft as per the requirement of your future employer. Type Rating can be done after the job selection or before as per the demands in the market.