The basic power flow (PF) problem calculates how much power should be sent around a transmission or distribution network in one time period (at one snapshot in time). It ignores how that power is produced.
Economic dispatch calculates how much power is produced at each power generator, ignoring the transmission network. Economic dispatch is a very simple but fast model. More accurate models use unit commitment in place of economic dispatch.
Optimal power flow (OPF) combines the power flow and economic dispatch problems. More advanced versions cover multiple time periods and replace economic dispatch with unit commitment.
The book "Power Generation, Operation, and Control" by Wood, Allen J. and Wollenberg, Bruce F. and Sheblé, Gerald B. is a reasonably good but not too formal reference.