Voluntarily Put $ In Pot — how often you put chips in preflop by choice (call or raise), not counting your free blind checks. A looseness gauge; ~24% is a solid 6-max baseline.
VPIP is the width of your starting-hand range. Way above baseline means you enter with too many weak hands and bleed chips postflop; way below means you fold profitable spots and become predictable. Read it TOGETHER with PFR — the gap between them tells you how much you flat-call versus raise.