The difference between two functions HHV and REF

Algos, strategies, code
1

what is the difference between following two functions, are both represents 10 bars high or 10 days high?

1 REF(HIGH,10) 

 2 HHV(10)

2

HHV will return the highest high value for the period you want. For example, for HHV(5), if the previous 5 candles high values are (8, 20, 9 , 15,19) then it will return 20.

REF(HIGH,5) will return the high of the 5th candle from current time. So in the above example the answer is 8.

3

Thanks, Which function should be used to get previous day OHLC values