If you don't already know the right answer for you, then its Apache!
Apache was (almost) the original web server, and runs over 50% of web server. Its Open Source, it has lots of modules, is easy to use, highly configurable, can be used with php, perl, java, python, etc, and most websites use it.
Some example differences:
- Apache uses a separate memory thread for each connection, that spends much of its time waiting for the next browser request (while still using memory). NginX uses a shared queuing system instead. Think of it as 1 till per customer, rather than a single queue of customers at a bank of tills.
- NginX has a server config file, where Apache can also have per directory ones. Thats great for individual developers to tweak there own project, but it means that the server has to check each directory in the path to a file each request - quite an overhead. NginX is faster, Apache is easier to use.
So, in summary
- for a typical web server, use Apache.
- but if you get millions of request a day, use NginX as the front end, Then Apache (or Node or whatever) as the back end application server.
By the way, the figures, from late 2016, that show the Unix/Linux Apache (50% +), and NginX ( ~ 20%) webserver growing, also show IIS (the Windows web server) fading to less than 10%. Most of the rest is taken by companies like Google, who run their own proprietary webservers.
If the figures were web traffic, rather the number of web servers, NginX would score much higher.