As a web developer myself, I have seen a lot of company using "online gaming" term to hide what they are really doing. What does it really mean?
If it is really about game, then they wouldn't need web developer that much. A simple website to introduce about their game is enough. However, when they are willing to pay a huge salary for web developer doing "online gaming", then you should know they are about something else.
Online gaming here actually mean online gambling. It requires customer to top up their game wallet, then use the e-money or credit to play online game, do sports betting, or play slot machines or some real human casino.
Some company only act as agent, the middle person between online gambling provider and customer. The agent will have plenty of online gambling provider, and the customer only need to top up via the agent, then they will let the agent know which online gambling platform they want to play.
Hence, no matter it is agent or the real online gambling provider, they will need web developer to handle their website, allow user to login, register, top up, check their threshold and convert them to premium user and so on. If online gambling provider is the one hiring, you get to work on the technology behind online gambling, which should be fun because you can find out how the algorithm actually works for slot game and sports betting.
The reason they use online gaming terms when they do hiring is because online gambling is illegal in my country. Using the word "online entertainment" will sounds a bit weird, kinda like porn or celebrity kind of stuff.. so online gaming is the best word to use. After all, gambling is still considered as a game.
If you are a web developers, fresh out from your studies and come upon this article, trying to find out if "online gaming" is a good and safe industry to work with or not, then you might be disappointed, because this article is not about that. However you can give your opinion at the opinion section below based on your experience if you have one.