Basically,gambling is not predictable it can be based on luck or by chance.We often say gambling is a game of luck,you might get lucky overtime but the probability of having much wins is majorly dominated by the chance.That's my favourable experience so far,the earlier we understand that Gambling happens unexpectedly the better for us.
Just like trading, gambling has different types, and each type can have a different nature. It has already been described by other friends above, but I would like to go ahead and throw my two cents about it as well.
When someone is into casino games, be it slots, dice, plinko, crash, roulette, or any other game you can think of, you can't rely on anything other than luck for you to win. Some people believe they can find certain patterns from the results of the last few rounds in a casino game and predict the next outcome. I say that is BS, and you can't predict anything based on that because the results are completely random, and a random result can't be guessed with accuracy.
On the other hand, sports betting is a type of gambling where your knowledge and experience play the biggest role, and luck only has cameos sometimes. If you have a lot of knowledge and experience about a certain sport, you will most likely have a pretty high success rate when you make bets on games of that sport, and occassionally, luck pay interrupt your momentum.