Both add one to i. They differ in what the expression evaluates to. i++ (post-increment) yields the old value, then increments. ++i (pre-increment) increments, then yields the new value. As a standalone statement (i++; vs ++i;) they have identical effect. The difference matters when you embed them in a larger expression: arr[i++] accesses arr[i] and then increments i, while arr[++i] increments first and accesses arr[i+1]. For loop counters, prefer the form that makes the side effect a single line, for (int i = 0; i < n; i++) is clearer than packing it into another expression.
Programming Fundamentals · Interview question
What's the difference between i++ and ++i?
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Operators
Everything between the variables: the symbols that combine, compare, and change values. Learn the four families and the precedence rules that bite.