Where you will find default conf file and what will be it's name in linux?

Ans: /etc/nginx/nginx.conf

Explanation of file

Ans:
let's see what has in this file
run this command
nano /etc/nginx/nginx.conf

You will get this output

user  nginx;
worker_processes  auto;

error_log  /var/log/nginx/error.log notice;
pid        /var/run/nginx.pid;


events {
    worker_connections  1024;
}


http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    keepalive_timeout  65;

    #gzip  on;

    include /etc/nginx/conf.d/*.conf;
}

let's explain line by line

user nginx; : This sets the user under which the Nginx worker processes will run. In this case, it's set to the "Nginx" user, it's enhance security by limiting the processes and permissions

worker_processes auto; : This will determine the number of worker process that Nginx will be handling for the incoming request. It will choose an automatic number of worker processes based on CPU.

error_log /var/log/nginx/error.log notice; : This will store your error log in the indicated location you can check here if you face any error during the run of the server.

pid /var/run/nginx.pid;: This file contains the master process ID. in a defined location.

events { ... }: In this section Nginx handle events like how Nginx handle connections and events like incoming request by default it has 1024 worker connections but you can change it as per your need.

http { ... }: This section actually handles all HTTP configurations for the server here we can include
include /etc/nginx/mime.types; which actually contain all types of file extensions like .jpg .png .txt .html ... etc. and
default_type application/octet-stream; this section set default MIME type that doesn't have an explicitly defined type.
log_format main here you can define the log format for every request.
access_log /var/log/nginx/access.log main; In this section, you can set the location and format for the access log file. It will keep every single request log with details.

sendfile on; by doing this you are giving permission to send file system calls so that static files can be served efficiently.

keepalive_timeout 65; In this section, you can set a timeout for keep-alive client connections. by default, it has 65 sec but you can set your own time.
include /etc/nginx/conf.d/*.conf; by doing this you can include additional configuration files from the /etc/nginx/conf.d/ directory. Basically, when you think your configuration script going too big you can separate by doing this.

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