Investopedia sums it up best:
Displaced Moving Average
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A moving average that has been adjusted forward or back in time in order to forecast trends. Displaced moving averages are constructed by taking the moving average and shifting it by a number of intervals, either positive or negative. If the number is negative, the displaced moving average will lag the original moving average, and if the number is positive the displaced moving average will lead the original moving average.
The aim behind displaced moving averages is to allow traders to center the moving average or make the displaced moving average fit better with the price movement, thereby removing some of the noise in the moving average. Some traders believe that displaced moving averages have more predictive power than basic moving averages such as simple and exponential.
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Offset is a synonym for "displacement" and also "shift".
The most famous use of dislpacement in moving averages is from Bill Williams' Alligator system. The Alligator attempts to capture large, sustained trends through a combination of displacement and triple moving averages. Theoretically, the combination of multiple averages displaced by varying degrees reduces the number of whipsaws.