What is the difference between Plot and Drawing.

For anything you see from an indicator on chart, it is either drawing or plot.

In most case, the default indicators come with the original release of a trading platform only have plot. For example, the lines or histogram of SMA, RSI, and MACD are Plot.

Drawing is usually refer to shape, special char and trend line. 

The main difference between Plot and Drawing is that Plot can be used by other functions such as Scan, screener and auto trading strategy. Drawing is for display purpose only, there is no value of the Drawing object can be accessed from other function.

For example, Auto trend line indicator doesn't have plot, it only draws trend lines on chart, so you cannot use it on scan, market analyzer or strategy. The trend lines from a divergence indicator are also Drawing object which cannot be used by other functions, we can only use the Plot(bearish or bullish signal) of the divergence indicator to create alert, scan or strategy.

The benefit of Drawing object is very obvious, we can use it to create more complex indicators, such as chart patterns or Volume profile. That's not what we can archieve with Plot only. Not all platforms support both Plot and Drawing, such as MetaStock, it only has plot, so it's impossible to create complex indicators on MetaStock.