This is a library module. It provides no out of the box functionality other then providing an API that other modules/code can use. Other projects might require/recommend this module. Install HTTPRL only if other modules recommend or require it.
What does httprl do?
Using stream_select() it will send http requests out in parallel. These requests can be made in a blocking or non-blocking way. Blocking will wait for the http response; Non-Blocking will close the connection not waiting for the response back. The API for httprl is similar to the Drupal 7 version of drupal_http_request().
As a bonus, a simple threading library is built on top of the parallel http requests functionality. This allows you to split a job and have multiple http "workers" running this split job in parallel. Anything that takes a long time to do can greatly benefit from using threads.
Session proxy is not a module: it is a replacement for Drupal core session handling API.
It acts as a proxy between fixed core procedural API towards a fully object oriented, more flexible and easier to extend session management API.
Basically, it strongly encapsulate the original API, separating user management against raw session storage: by using it you are able to implement any session storage engine (memcache, redis, ... ) without handling cookies and by users yourself.