First things first: depending on the ingenuity of a specific software provider, there may be a variety of paying symbols and ways to execute them. But their vital function in the distribution of wins is what ties them all together. So to speak, paying symbols exist to enable winnings hierarchy and, as a consequence, increase the variety and excitement of the gaming experience (opposite to classic casino games).
Such a bizarre winnings distribution scheme would not be conceivable without the presence of so many different paying symbols. I'm referring to a scenario in which you might wager 1 EUR per spin and have the chance to win 0 EUR, 1 EUR, or even 10,000 EUR on some video slots (and many other outcomes somewhere between).
Regular paying symbols are frequently represented by card values. For instance, the payment symbols A (Ace in card games), K (King), Q (Queen), J (Jack), and T (Ten) are frequently employed. Although these are not the only ones used in standard symbols. A specific slot game's main characters also function as regularly paying symbols (each online slot has its own).
The lowest earning symbols in the game are always those that pay out regularly (in comparison to Special symbols). There are, however, a few rankings among them as well. Standard symbols are therefore not equal and pay much differently (according to paytable).
Regular paying symbols must always line up in a specific pattern (referred to as a pay line) in order to produce a winning, whereas Special symbols are not always subject to these limitations (will be discussed further). In other words, Regular symbols are always used to pay by lines (99% of the time). They are significantly different from Special symbols in this regard, and I would characterize them as being quite primitive.
They are spread out fairly widely. 8–10 regular symbols are a common occurrence in online slots, particularly on more recent ones.
The Scatter, Wild, and Bonus game symbols are the only ones that really exist. Therefore, Special symbols are less common than Regular symbols.
The highest earning symbols in the game are, as you might have guessed, special symbols. Due to their great value, there aren't really many of them because of their scarcity.
When they create an eligible pay-line, special symbols not only pay out by themselves but also activate extra features in an online slot machine (such as: Free spins, Bonus game, Multiplier, etc.). And in the game, this is their primary objective.
Additionally, unlike Regular symbols, Special symbols do not always need to create a line. For instance, it is not important where a Scatter sign or Bonus game symbol appears on the screen as long as they do so in a predetermined number (often at least three).
It is rather foreseeable that special symbols are typically well-designed and animated. The main character of the slot machine's story is frequently referenced and shown on special symbols.
How much of paying symbols do online slots have on average
Modern online slots often offer 8–10 Regular paying symbols (of which 4-5 are card values + 4-5 are plot characters) and an additional 2–3 Special paying symbols. In addition, I would point out that 95% of the available online slots readily fit into this category. These figures are therefore very typical.
Where to learn about paying symbols in a particular slot
You must navigate to the "Info" area, which is included on practically every online slot machine. Simply click on it, if necessary scrolling a few pages, and you'll be able to see what the paying symbols are for this specific slot machine and how much they pay.