HTTP/2 is a version of an HTTP networking protocol used for communication over the internet. It is more efficient than HTTP 1.1 as it uses a single TCP connection for sending multiple requests and responses simultaneously thanks to multiplexing.
HTTP/2 is calable of streaming data over the TCP connection in parallel which each request/response tagged with stream ID so that client can associate requests with responses and enable out-of-order delivery.
HTTP2 is capable of compression headers and data which can save the costs and improve performance.
It is also capable of pushing from a server which allows to send other resources to the client before client requests them. It can be helpful to reduce loading and by pre-sending required files (e.g. CSS or JS files).