nginx serves files from two different directory on one server

The simplest solution is where you have total control over the filesystem and URI name spaces, so that the application in /path/to/root/foo/index.html is accessible using the URI /foo/ and the application in /path/to/root/bar/index.html is accessible using the URI /bar/.

In this case, no location blocks are necessary, and the value of root is /path/to/root because the pathname of the file is constructed by concatenating this value with the URI. See this document for details.

For example:

server {
    server_name example.com;
    root /path/to/root;
}

The above server block will fine application foo at http://example.com/foo/ and application bar at http://example.com/bar/.

In the case where the top level directory element has a different name to the top level URI element, you will need to use an alias directive within a location block. See this document for details.

For example:

server {
    server_name example.com;

    location /foo/ {
        alias /path/to/foos/directory/;
    }
    location /bar/ {
        alias /path/to/bars/directory/;
    }
}

Both the location value and the alias value should end with /, or neither end with /.

Note that the location directive is used without the = operator, which is only used to match a single URI. See this document for details.