What Does Seamless Interface Mean?
A seamless interface is two computer programs that are carefully joined together so that they appear to be a single program with a single user interface. A seamless interface will conceal the fact that it is created from two different programs, even if those programs were written by two different programmers.
Techopedia Explains Seamless Interface
In software technology, concealing the seam is of prime importance. The aim of any application integration is to provide a seamless interface. This is achieved by developing a back-end program interpreted as a single user interface. This single, transparent user interface may in turn contain many programs hidden in the background, of which the user has no knowledge. The programs in the background may be written by several different programmers at different locations and at different times. The programs are distributed over the network, and are screened to isolate the user location and data.
A seamless interface allows one program to integrate with another while still allowing the user to access both programs.