The budgeted cost of the work actually completed at a given date. Earned value prices finished work at baseline rates, never at what the work really cost.
Earned value answers how much work is done, expressed in money. The project level formula is the budget at completion multiplied by the proportion of work genuinely complete, so a £500,000 project that is 30 percent finished has earned £150,000. Pricing at baseline rates is what makes the figure comparable in two directions at once: set against planned value it gives schedule variance, set against actual cost it gives cost variance.
See also
The budgeted cost of the work the baseline scheduled to be complete by a given date. Planned value = budget at completion × planned percent complete.
The costs genuinely incurred for the work counted as earned value, up to a given date. Actual cost only means something when it covers the same scope earned value covers.
Where this comes up
Two ratios off one earned value figure. SPI divides it by the plan and reads schedule. CPI divides it by the bill and reads cost. Below 1 is bad news in both, for different reasons.
Three figures read at one date. Planned value is what the baseline said would be finished by now, earned value is what did finish, actual cost is what finishing it cost.