N-Tier Architecture

Multi-tier architecture (often referred to as n-tier architecture) or multilayered architecture is a client–server architecture in which presentation, application processing, and data management functions are physically separated. Using an N-tier architecture, web developers can create modular applications.
Common layers
In a multilayered architecture the most common used layers are:
Presentation layer - the visual part of a web application
Application layer - the server-side of a web application 
Database layer - the persistence layer where information is saved and updated 
Presentation layer
This layer handles the user interaction. This part of the application is usually built-in HTML and Javascript in various technologies and frameworks:
​React - the popular Javascript framework built by Facebook
​Vue.js - The Progressive JavaScript Framework
​jQuery   
Application layer
Represents the server-side of the application and can be developed in many programming languages:
​Php (the most popular server-side language ) using Laravel, CodeIgniter​
​Python server-side apps can be developed using Django, Flask​
​Ruby​
Database layer
The majority of web apps requires a type of storage to save the relevant data:
​MySql - the popular open-source database engine 
​SQLite - the lite version of MySql
​MongoDB - a document-based engine
​
Common Architectures
In web development the most used architectures are:
​Single Tier architecture​
The web application is served only once by the server, and runs entirely on the client-side - read more​
Single Tier architecture
​Two Tier architecture​
Sometimes named Full-Stack architecture - read more​
Two Tier architecture
Links & Resources
​Multitier Architecture - Wikipedia page 
​N Tier Architecture - a comprehensive article (with samples)
Techopedia One-Tier Architecture - blog article
Techopedia Two-Tier Architecture - blog article 
​Single-Tier vs. Multi-Tier Architecture - a comparison of concepts 