- When I’m going to do a project how I can know what language(s) to use?
Your browser only understands HMTL, CSS and Javascript, languages like Ruby, PHP, Python, etc., will generate code that browsers understand.
- What one language does that another does?
Hard to compare backend languages, practically today, all backend languages can do the same thing, the difference is that in some a task can be easier and in others more difficult.
- Which language is best for each situation?
If you work with high performance in the backend look for languages like Scala, Java, Erlang. If you’re developing projects you need to develop quickly use PHP, Ruby.
- What is the order in which I must declare them?
Start with HTML, it will be the structure of your project (imagine a building, first build the structure. Then style your HTML with CSS (finish). Add Javascript behavior, effects, transitions, callbacks, etc... Finally create communication with the database through languages such as PHP, Ruby, Python, etc...
- What triggers each of them? What does it take for each of them to start? Do they all start together? Do they start separately? Which one starts first? What is the best order to place them? Or it depends on how you program?
When a user opens a browser and enters a URL, the server receives this information (probably on port 80, http) and initializes the HTTP server (apache, Nginx, etc.), this server communicates with the application and tries to resolve it by returning a response. There is a life cycle for each request, can be complex or not.
- How do I know when to use each one? (Can you give examples? This is very important to me).
This is perhaps the most difficult question, it depends very much on the purpose of your project. Start at the basics, and evolve your project according to need.
I hope I helped, the questions are very generic and difficult to answer.
The question is broad and asks for opinions. It does not ask a lot of things together. Read [tour] and [help] to better understand what types of questions are acceptable.
– Maniero
Your questions are very reasonable, but if you put them all together in one question, it’s just hard to answer. Take a look here: http://answall.com/a/25215/129 and here: http://answall.com/q/35547/129
– Sergio