Reels, rows & paylines
Reels are the columns that display symbols. Rows are their horizontal positions. A payline is a defined path on which eligible symbols can form a win. More paylines do not automatically mean a higher theoretical return.
Wilds & scatters
A wild often substitutes for another symbol in eligible combinations. A scatter can trigger a feature or a payment without appearing on a conventional line. Exceptions belong in the individual game’s paytable.
Tumbling reels & cluster pays
Tumbling removes winning symbols and fills the space again. Cluster games form wins from adjacent groups. These describe different parts of a game: a cluster game may also use tumbles.
Multipliers & sticky symbols
A multiplier changes a qualifying value according to the rules. A sticky symbol remains for a specified number of spins or a feature. Neither term says anything by itself about the chance of a win.
RTP, volatility & house edge
RTP is a theoretical long-run return. Volatility describes the variability of outcomes. House edge is the complement of RTP in a simple model. None tells you the result of an individual session.
Fixed prizes & progressive jackpots
A fixed feature prize is defined in the game’s rules. A progressive jackpot grows according to its contribution system. Read the eligibility rules; do not assume that any display labelled “jackpot” is a network progressive.
Sources & further reading
Source review: . Availability and terms can change.