Handicap Calculator
The HI is the golfer's current Handicap Index (the "raw" handicap value taken to one decimal figure). CH means Course Handicap, and is the whole number indicating the number of strokes the golfer receives from the course / tee chosen. PH is Playing Handicap, and can be different from the CH if the golfer's number of strokes are reduced due to a format of play, or if an adjustment is made when two or more tees are in play with different pars. Note that the PH will change if you tap on the Handicap Allowance percentage to take it down from 100%, which you would commonly do in a format such as a team event. For example, if the Allowance is 90%, and the low handicapped player has a CH of 12, it will be reduced to 11; the higher handicapped player's CH is 24 and 90% reduces them to a 21.
SO means Shots Off, and references the number of strokes given / received for the match.
For example, two golfers are playing each other in a match; the lowest CH is 12, and the opponent's CH is 24. The 12 shows SO as 0, and the 24 shows SO as 12. This means that the match calls for "spinning off the low" handicapped player for equity. The 12 plays at zero and the higher handicapper receives the difference between the two players, which is 12 strokes.