Before starting this tutorial, I just want to say that we will learn LWC with real time project works (which we will start from 4th tutorial), so that it make you understand well and how it will be helpful in any project.
Lightning Web Components is the Salesforce implementation of that new breed of lightweight frameworks built on web standards. It leverages custom elements, templates, shadow DOM, decorators, modules, and other new language constructs available in ECMAScript 7 and beyond.

Lightning Web Components provides a layer of specialized Salesforce services on top of the core stack, including:
  • The Base Lightning Components, a set of over 70 UI components all built as custom elements.
  • The Lightning Data Service which provides declarative access to Salesforce data and metadata, data caching, and data synchronization.
  • The User Interface API, the underlying service that makes Base Lightning Components and the Lightning Data Service metadata-aware, leading to substantial productivity gains.
Aura Components vs Web Components
Aura Components, leveraging its own component model, templates, and modular development programming model.
Lightning Web Components, built on top of the web standards breakthroughs of the last five years: web components, custom elements, Shadow DOM, etc.

Aura components and Lightning web components can coexist and interoperate, and they share the same high-level services:
  • Aura components and Lightning web components can coexist on the same page
  • Aura components can include Lightning web components
  • Aura components and Lightning web components share the same base Lightning components. Base Lightning components were already implemented as Lightning web components.
  • Aura components and Lightning web components share the same underlying services (Lightning Data Service, User Interface API, etc.).
If you are already developing Lightning components with the Aura programming model, you can continue to do so. Your Aura components will continue to work as before. You can build new components with Aura or Lightning Web Components. Your Aura and Lightning Web Components can coexist and interoperate. Over time, you can consider migrating your Aura Components to Lightning Web Components, starting with the components that would benefit the most from the performance benefits of Lightning Web Components.

If you are new to developing on Lightning or if you are starting a new project, we recommend using the Lightning Web Components programming model.