Shift can be used to adjust an indicator forward or back in time to "better" forecast trends or better fit the candlestick movements of a chart. In MT4, you can use indicators that are equipped with a Shift option to adjust them so that the indicator better aligns with the chart's candlestick Highs or Lows etc.

Shift makes an indicator's lag worse, though. A negative Shift can reduce lag, but it's questionable as I've personally noticed it only looks good historically.

Shift basically moves the value of the Moving Average in time.

For example:

• The current (forming candle) has a SHIFT value of 0.
• The previous candlestick before that has a SHIFT value of 1.
• The candlestick formed before that one has a shift value of 2, and so on.

PS: Shift is also called DMA or Displaced Moving Average.

PPS: Below is an example of a 10-period Moving Average with and without Shift applied.