The phrase "internship period" refers to a specific amount of time when someone works as an intern, gaining practical experience and learning about a particular job or industry. Full definition
This is a 3 month internship at # 18,000 with the view to move to # 20,000 up on successful internship period. (inspiringinterns.com)
The standard internship period these days is approximately 10 - 12 weeks, predominately focusing on the summer months. (campus-to-career.com)
At the end of the 3 - month internship period she had to make a decision between joining the ECI Development team permanently, or chasing her dreams in Panama with the US Peace Corps. (ecidevelopment.com)