Meaning of “inside” - Learner’s Dictionary

inside

adjective uk us /ˌɪnˈsaɪd/

B2 [ always before noun ] in or on the part of something under its surface:

Put your wallet in the inside pocket of your jacket.
inside information/knowledge, etc

information that is only known by people who are part of an organization, group, etc:

I needed someone with inside knowledge to back up my story.

(Definition of “inside adjective” from the Cambridge Learner’s Dictionary © Cambridge University Press)