The pseudorandom number generator (PRNG) is a math function. There are many types. One type is the "Center-Square" method. Start with a seed, that is, a binary number (typically 64 bits), square it (multiply it by itself). This results in a 128-bit number. Take the center bits (i.e., bits 32 through 95), shift them down, and use that as your random number and as the seed for the next random number. That's not a very good method.
A better method is "Multiplicative-Congruential." Start with a seed, multiply it by a constant that will usually cause overflows. Ignore overflows, divide that by another constant which does not have a common divisor with the first constant, and use the remainder as the new number and as the seed for the next iteration. I believe that the method used in most gambling machines.
That is also the method used in Optimum Video Poker, but the random numbers are NOT used to select cards. Instead, they are used to shuffle the deck many times before each hand is dealt. I defy anyone to detect a pattern in the dealt hands.
So what does it matter whether a number is random or pseudorandom? Many years ago a new casino opened in Canada (I think it was in Windsor). By law, it had to close for several hours every night. The keno game used a PRNG. Everything was fine until one very astute player got a 20 out of 20 win, then a 19 out of 20 win, before they really dug in to find out how he did it. At first he said he used chaos theory. Then he admitted that he had noticed that the games were identical every day. It turned out that the keno computer was shut down when the casino closed, and every morning the PRNG started with the same seed, no naturally the results were the same every day. All they would have had to do was use some seed that wasn't a constant. Even the date would have been OK.
So for all practical purposes, the difference is in how the "random" numbers are used.