One of the simpler ways to embed an STL model onto your webpage is to use an STL viewer embedding tool.
Push the STL file to your Github repo, paste the link to the file into the field in part 1, copy and paste the iframe code generated in part 2 into your HTML document.
You can easily customize the color of your model, the background, shading, and other display aspects with this tool.
You can interact with the model in this viewer, (zoom, rotate, etc.)
To embed a Fusion 360 model onto a website, go to your project hub,
Create a project and upload your STL model
Once it's uploaded, click on the file and then select the "Share" icon.
Select "Embed".
Select the size.
Copy the code and paste it into the code of your website.
You can manipulate the model in this viewer too but it has many more features than in the first example, (the ability to measure, orient, change opacity, etc.)
This last example is the most powerful/customizable but also complicated way to embed 3D models onto your webpage. Three.js is a JavaScript library used to create and display animated 3D computer graphics in a web browser using WebGL. You must include different Javascript modules in your repo and establish at least a "scene", "camera", and "renderer" in your HTML document in order to render/display anything. There are also some hurdles if you want to run things locally.
There are many tutorials [1]
[2]
[3] on how to get started but I recommend checking out the examples on the official three.js page to get a sense of its capabilities.