How does the browser connect to the server and how can these connections be viewed?

Question

Nginx

Hung up stub_status on; to one of the ports.
Now I open the specified port and see the statistics, where the first of the Active connections parameters is: 247.
Please explain what these connections are?
As I understand it, the browser connects to the server, opening a connection, receives the necessary data, then the connection is closed. Or does it not close and is open for a while? If so, what time?
Is 247 the number of connections on which data is being transmitted right now?
UPD: Do I understand correctly that if I have 1 css file and three pictures on the page, in the case of using http2, all this will be transmitted over one connection, and otherwise, 4 connections will be opened?

Answer 1

many connections only say that the system lives and exchanges information with the world. you can understand what this figure means after trials in the system and method of counting statistics.
half-closed tcp connections or something else may well be taken into account.
again, in addition to your web server, the system exchanges some information with the world and can create additional connections.
read and understand what, where and where. a number is just a number.
UPD: this is probably about the extension of the SPDY protocol with a method of packing several files into one connection.