The interior of a building or vehicle is the inside part of it.
Interior is often used as an adjective in front of a noun to refer to an inside part of a building or vehicle.
You do not usually use 'interior' to refer to the inside parts of other things. Instead you use internal.
Adj. | 1. | internal - happening or arising or located within some limits or especially surface; "internal organs"; "internal mechanism of a toy"; "internal party maneuvering" inside - relating to or being on the side closer to the center or within a defined space; "he reached into his inside jacket pocket"; "inside out"; "an inside pitch is between home plate and the batter" external - happening or arising or located outside or beyond some limits or especially surface; "the external auditory canal"; "external pressures" |
2. | internal - occurring within an institution or community; "intragroup squabbling within the corporation" intramural - carried on within the bounds of an institution or community; "most of the students participated actively in the college's intramural sports program" | |
3. | internal - inside the country; "the British Home Office has broader responsibilities than the United States Department of the Interior"; "the nation's internal politics" domestic - of concern to or concerning the internal affairs of a nation; "domestic issues such as tax rate and highway construction" | |
4. | internal - located inward; "Beethoven's manuscript looks like a bloody record of a tremendous inner battle"- Leonard Bernstein; "she thinks she has no soul, no interior life, but the truth is that she has no access to it"- David Denby; "an internal sense of rightousness"- A.R.Gurney,Jr. inward - relating to or existing in the mind or thoughts; "a concern with inward reflections" | |
5. | internal - innermost or essential; "the inner logic of Cubism"; "the internal contradictions of the theory"; "the intimate structure of matter" intrinsic, intrinsical - belonging to a thing by its very nature; "form was treated as something intrinsic, as the very essence of the thing"- John Dewey |