Flooding does not require the use of paths, but most protocols employ them for efficiency reasons.
Each node along a path will know something of the overall condition of the path (e.g., quality of service, delay, energy levels); this knowledge may be used in updating the paths to be used in subsequent message exchanges
single path algorithms: one path is computed for each source-destination pair. The most popular of these is the shortest path algorithm, in which the path that leads to the least cost (energy, latency) is used.