.net MVC is framework for building server html form based application using a modified variant of the well known MVC pattern.
you define a render and post back model (in most examples they are the same)
you define a action that receives model (form post), processes it and sets a modified model to the view
you define a view to render the model as html.
MVC routing map a request (form post or get) to an action and bind the request data to the action parameters. The action process the request data, creates a view model and calls a view. The view renders the html. repeat
MVC can also be be used to implement webapi request handling. rather than render html, the request return data typically in xml or json format.
an alternative is to build the application in javascript, and make ajax calls to the server (typically webapi in .net). knockout.js is a binding framework to implement the MVC pattern in javascript. it supports two way binding to html elements.
in knockout, there is a true observable model defined by MVC pattern. updates to the model, trigger events that redisplay the view (knockout does this via binding). view (dom events) update the model. again knockout supports binding element events to the model. in the model you define event handlers that are called to process model changes. these model event handlers will use ajax to update the server with model changes.
one disadvantage of knockout is it is only the binding library and model, it does not have a view engine, you must pick one, or use simple dom elements. If you pick a view library like kendo ui, it has its own two-way binding package and knockout is not required (knockout support is mostly to kendo-ui to an existing knockout application).
there are two types of javascript applications. SPA (Single Page App), where the javascript code intercepts navigation, and there is really only one website page. MPA (Multiple page applications), where each website page is a separate application. knockout supports SPA if you add a navigation library.
for building javascript applications, there are more full featured frameworks, and knockout is not typically selected for new projects. as you are just starting out, you might be better served picking a more opinionated framework. the most popular javascript frameworks are:
react.js
vue.js (easiest for MPA)
angular
note: there is also blazor SPA which you code in C#