The OpenBazaar program is actually two programs in one.
- OpenBazaar server - The server is the back end application which allows OpenBazaar to function. Each user runs a server to connect them to the network.
- OpenBazaar client - The client is the front end application and allows the user to communicate and control the server. The client is the visual interface; it's what you're looking at when you run OpenBazaar.
In order for a vendor's store and listings to be visible to other users on the network, your OpenBazaar server must be running and connected to the internet. The client doesn't need to be running, though without the client you may not know when you receive an order or messages from other users.
A buyer doesn't need to run their server continually since they aren't offering listings. However, they are encouraged to run it as often as possible when they are engaged in transactions since they will not see updates on their purchases until they are connected.
By default, the OpenBazaar packages and installers will install both server and client locally on your machine. However, you can choose to run the server elsewhere.
The client is run on the user's own computer to connect to their server, but the server doesn't need to be run on a user's own computer. You can run your server on another computer such as a Raspberry Pi or use a virtual private server (VPS) to host your store for you.
For more information on how to connect to a remote server, [read this post]. If you'd like a guide to running OpenBazaar on a VPS, visit this article.