The integral mesh and the mesh associated to test functions or unknown functions can be different in the case of varf form

Dear all,

I read from the FreeFem document (page 202, release 4.6) that " The integral mesh and the mesh associated to test functions or unknown functions can be different in the case of
varf form". I am wondering what this means? for example, if we have two overlapped meshes Th and Ths, and

fespace Vh(Th, P1);
Vh u, v;

fespace Vhs(Ths, P1);
Vhs us;

varf a(u, v) = int2d(Th)( u*v) + int2d(Ths)( u*v)

Would the above integral gives the following discretised form automatically:

(A + P’ * B * P ) * u = f

where us = P* u with P is the interpolation matrix between mesh Th and Ths, A and B are discretised matrices from Th and Ths respectively?

Best,
Yongxing.