Answer 1

One is on the client. The other is on the server..........

Okay, let me start over. Client-side is your end-users, your customers, the people that are going to be using your software for whatever purpose it holds. They will install software on THEIR end and use it locally on their computer. Client-side software is typically what is used to connect/access the server-side stuff. Server-side programs are stored on a server and is usually a centralized software that interacts with clients.

Think about it in terms of a chat program. You have all of your individual users (clients) that downloaded the chat software to their computer (client-side program). Each client will connect to the server, and the server will relay messages between all of the clients. So the server-side program in this instance is a program on the server that regulates communication between all of the clients that connect to it.

When you access a website, you're using client-side program (your web browser) to send requests to the server, and it's the server that's responding by sending the website to your browser.