This is perhaps best answered in the context of a specific model.
Take the standard growth model. The resource constraint is $I + C = A F(K, L)$.
This R.C. is a description of a technology. It maps inputs (K and L) into feasible outputs (I + C).
So, a technology describes how inputs can be transformed into outputs.
The outputs need not be goods (in the traditional sense of stuff you can touch).
The $A$ part in the R.C. is a productivity term. In specific models, changes in $A$ are due to changes in available technologies (e.g., R&D driven growth models), but more generally differences in $A$ across, say, countries, could be due to other things (e.g., institutions).