The interior of the building was very spacious.
内部の情報が外部に漏れた。
Internal information was leaked to the outside.
The police inspected the interior of the building.
A conflict is occurring within the company.
Unauthorized people are not allowed to enter the interior.
It's necessary to reform the organization from within.
内部 is a general term meaning 'inside' or 'interior', while 内情 specifically refers to the actual state of affairs within that interior.
内部 is a more formal, technical word for 'interior', used for machines, organizations, or structures, whereas 中 is the everyday word for 'inside'.
internal method; inner workings; internal resources
internal processing