Confused about load balancing and horizontal scaling in postgresql

Please correct me if I am wrong but I guess handling more requests and load by adding more machines or balancing the load between multiple servers is horizontal scalling. So, if I add more servers, how do I distribute the database? Do I create one database to hold the user records with multiple servers? Or do I split the database too? What about database integrity? How to synchronize it? Or else what do I do? I am a newbie and really confused but eager to learn. I would like to use postgres for my project and would like to know some basic things before I start. I was thinking of using two small ec2 instances. But I got confused about the database. How do I go about creating the database. Do I need to go through sharding for this? What would be the best approach for horizontal scaling in accordance to postgres. I would really appreciate if you could explain it to me. Thank you! **Edit:** How do I load balance using multiple machines and manage the database? I have an app where users can upload videos and it will be converted to mp4 using Elastic Transcoder. Users about 10k. So, how do I load balance using multiple machines and manage the database? What I want to do is load balancing for the performance. And I read in many post that adding more machine can leverage it. So I though of horizontal scaling. But since horizontal scaling is scary, how do I load balance and manage my database?