Web games, games that run in the browser, and that normally have minimal load time.

History

In the early web there were Java applets, browsers could load and play them, and there were communities of applet developers and applet game players.

And then there was what was known as flash, a plugin that every browser supported. From about 2006 to 2010 flash games boomed, overshadowing any other form of browser game.
Games such as angry birds were born out of that era.
By 2017 browsers began to no longer support flash,
as of today it is no longer supported,
and many of the communities associated with flash games
have grown thin.

Web games are now generally made with HTML5 and JavaScript,
using the HTML5 canvas element one can make games by drawing and redrawing on it. Communities that survived from the flash era,
such as Newgrounds did so by accommodating the new HTML5 format.

Business

During the flash era there were many sites one could upload your flash games to and get paid from the site simply for number of views. Today there are sites such as Gamemonetize, CrazyGames, Poki for direct monetization of HTML5 games and a community of developers that make many games for those sites. During the flash era there were at least 100 such sites of equal caliber, today only a handful.

But there are other ways one can generate income from a HTML5 game. One of the best ways is to make a multiplayer browser game.
People like interacting with other people.
And you simply place ads during the game, your game operates just like a website and because of the multiplayer nature, each new player drives even more new players to the game.

Another general way is to have links in your game,
simply distributing the game on all possible places
will generate views of your site, and on that linked site
you can have your own ads.

HTML5 games can also be easily packaged as Android applications,
using a little Java you can compile your game into an apk.

Also an HTML5 web demo is a great way to advertise a larger
console or laptop/desktop game.

Programming

Today one of the most popular tools for making web games is Unity.
Other tools include Godot and Construct.
If you feel comfortable using C# in Unity,
you will likely also feel comfortable making a game from scratch
using just JavaScript and HTML5. And there are libraries
that aim to reduce the amount of JavaScript code you will need such as Phaser and Tads Basic Game Objects

For basic 2D games you no longer need to utilize webgl,
a regular 2D canvas will perform well in modern devices.
Therefore using just JavaScript and HTML5 to make a game
can be easy and rewarding.

For a multiplayer back end, you have many options
such as Socket io or to simply communicate with a server using your language of choice and HTML.

Fun

Ultimately making any game is fun, and web games are a good place to start if you've never programmed a game before.