It is a bit critical question but the answerr is very 
simple .....he want to know the Flow of your project in 
which he trie sto expoler the HLD, DLD, LLD so u make a 
overiew of the project and tell him how is the flow of data 
from one module to another module and what are the 
submodulepresent into it and how the data is given to the 
submodules 

Here the interviewer asking question about the architecture
of ur project that means architecture are of three types
they 1-tier, 2-tier and 3-tier architecture. This will be
mentioned in CRS or SRS.