Basic Terms

RNG (Random Number Generator)

The core component of every slot machine, ensuring that each spin’s outcome is completely random and independent. All licensed slot machines must use an RNG certified by a third-party testing lab.

RTP (Return to Player)

The theoretical percentage of all wagered money that a slot machine returns to players over time. A 96% RTP means that for every $100 wagered, $96 is theoretically returned in the long run.

House Edge

100% minus RTP equals the House Edge. 96% RTP = 4% House Edge. This is the operator’s theoretical profit margin.

Volatility / Variance

Describes how payouts are distributed. Low volatility = frequent small wins; high volatility = rare big wins. Essentially the flip side of Hit Frequency.

GGR (Gross Gaming Revenue)

Total player wagers minus total player winnings. The core metric for measuring operator revenue.

NGR (Net Gaming Revenue)

GGR minus bonuses, taxes, and provider royalties.

Game Mechanics

Paylines

Traditional left-to-right win lines. Classic slots typically have 1–5 paylines, while modern video slots can have 10–50 or more.

Ways to Win

243 Ways, 1024 Ways, etc. Any matching symbols on adjacent reels count as a win, regardless of position. More flexible than paylines.

MegaWays

A patented mechanic invented by Big Time Gaming. Each spin randomly varies the number of visible symbols per reel, creating up to 117,649 win ways. Licensed to multiple providers.

Cluster Pays

A group of adjacent matching symbols (usually 5 or more) pays out. Signature game: Reactoonz.

Cascading Reels / Tumble

After a win, the winning symbols are removed and symbols above fall down to fill the gaps, potentially triggering consecutive wins. A core mechanic in games like Sweet Bonanza and Gates of Olympus.

Scatter

Doesn’t need to land on a payline — appearing anywhere on the reels (usually 3 or more) triggers bonus features or free spins.

Wild

Substitutes for other regular symbols to help form winning combinations. Similar to a wild card in poker.

Expanding Wild / Sticky Wild

Expanding Wild stretches to cover an entire reel. Sticky Wild stays in place during free spins, remaining until the bonus round ends.

Multiplier

A factor applied to winnings. A 5x Multiplier means your win is multiplied by 5. In some games, multipliers can stack to extremely high values.

Bonus Features

Free Spins

The most common bonus feature. Usually triggered by landing 3 Scatters, granting a set number of free spins with potential enhancements (multipliers, special symbols, etc.).

Bonus Buy / Feature Buy

Pay a set amount (typically 80–100x the bet) to skip the base game and go directly to the bonus round. Banned in some jurisdictions (e.g., the UK).

Gamble Feature

After a win, you can choose to “double or nothing” — a 50% chance to double your win or lose it all.

Progressive Jackpot

A small portion of each bet is contributed to a prize pool that grows continuously until someone wins it. Signature game: Mega Moolah (record jackpot exceeding 20 million euros).

Re-trigger

Collecting enough Scatters during free spins to earn additional free spin rounds.

Industry Terms

Aggregator

A platform that integrates game content from multiple providers into a single API, allowing operators to access thousands of games through one integration. Examples: SoftSwiss, EveryMatrix, SoftGamings.

PAR Sheet

The math model document for a game. Contains detailed records of symbol distribution, pay tables, RTP calculations, and other core data. Considered a trade secret by providers.

Provably Fair

A cryptographic fairness verification system. Players can verify after each round that the result was not tampered with. Common in crypto casinos, using algorithms like HMAC-SHA256.

Responsible Gaming

An umbrella term for industry self-regulation and regulatory requirements, including self-exclusion, deposit limits, cooling-off periods, and other player protection measures.

B2B / B2C

B2B (Business to Business): Provider to operator — e.g., Pragmatic Play supplying games to a casino. B2C (Business to Consumer): Operator to player — e.g., Stake.com serving end users.

Certification / Testing Lab

Independent testing laboratories such as eCOGRA, GLI, and BMM Testlabs, responsible for certifying RNG fairness and RTP accuracy.