It is called a ternary operator. There are a few component

1. the assignment

max =

1. the condition

max < h[tempChar - 97]

1. if the condition is true, then return

h[tempChar - 97]

1. if it is false, then return

max

So it is functionally identical to

if (max < h[tempChar - 97]){
    max = h[tempChar - 97];
} else {
    max = max;
}

Personally I think it is a little redundant in this specific use case, but it can certainly be useful at times.