These themes can be varied, and among the most popular are those related to animals, ancient Egypt, sport, and gems. In other words, slot machine themes give you an idea of what topics, genres, or motifs to expect from a slot game’s design. Themes are to slots as flavours are to ice-cream. Getting into the nitty gritty of how a slot’s RTP works or how slot paylines work can help you get better insight into this ever-popular type of casino game. Much like those at brick-and-mortar casinos, video slots are operated by a random number generator (RNG), which ensures that the outcomes remain random and fair for players. They derive their name from the slots they have for players to insert coins and retrieve winnings. Video slots are multimedia versions of the iconic slot machines you’ll find at practically every casino out there. Final Word on Online Casino Slot Themes.The Best Slot Developers for Online Slot Themes.