We call the conversion from a continuous time signal $f(t)$ to a discrete time signal $f_s[k]$ "sampling". Is there a name for the reverse operation, i.e. creating a continuous time signal from a discrete time signal?
In mathematics it is called interpolation. If you fill data in between data points (in signal processing we call them samples) it is called interpolation. If you try to fill missing data outside the range of the collected data/samples, it is called extrapolation. In signal processing, the operation of filling the data in between samples is called interpolation and the blocks that do this operation are called interpolation filters.