Spot price
The current market price of the underlying stock, ETF or index, as opposed to a strike price or a futures price.
The spot price is what the underlying trades for now. Option values, deltas and moneyness are all measured against it: a call is in the money when the spot price is above its strike, and out of the money when it is below.
On a GEX chart the spot price is the reference for everything else. The regime compares it with the gamma flip, and the strikes nearest to it carry the bulk of the gamma close to expiration. CaymanBot's GEX view tags the strike nearest the spot price SPOT, so the tag sits on a strike, not on the exact price.
Illustrative example (hypothetical numbers, not a real trade): a stock's spot price is $50.40. A 50 call is $0.40 in the money and a 52 call is $1.60 out of the money. A GEX chart with $1 strikes would tag the 50 strike as the one nearest the spot price.