O que determina se um PC é capaz de ser um servidor da Web ou não?

I have some questions about using a computer as a web server. Why can certain computers act as a web server and what features make them able to do so? Are there any cases where a computer is unable to act as a web server?

Pretty much any computer can be used as a web server, provided it can connect to a network and run web server software. Since a web server can be quite simple and there are free and open source web servers available, in practice, any device can act as a web server.

The bigger problem is the networking side. In order for a system to act as a server, other machines need to be able to access it. If it is just for use in a LAN setup, there are no concerns. However, if it is for use with the wider Internet, then data needs to be routed to it. This requires either a static IP address associated with the server (or port-forwarded through a router) or an external service which can map a domain name/subdomain to a changing dynamic IP address.

For what it is worth, you can buy $10 computers that are capable of acting as a basic web server. Of course, while any device can act as a web server, the functionality of websites can vary hugely, and a cheap device (or slow connection) may not be able to keep up with the demand depending on what the specific website is.

Note that everything above talks about web servers, but the same can be said for pretty much any type of server.