When you are part of Netsukuku you are enabled to offer a service to your friend with your own computer. Your device receives a unique address which is reachable from anywhere in the network. Then, thanks to a distributed naming service, your device can register a human-friendly hostname without asking for permission to any central authority.
When you connect to the Internet your ISP usually gives to you a private address (NAT) and translates it when you contact a public server. This is needed because of the centralized topology of the network, because each provider gets a scarse number of addresses to administer. That means that you can connect a public server, but no one else can initiate a connection to your device.
Further, even if you get a public address (IP) from your ISP, you would have to register a easy-to-remember domain with an authority, which will cost you more money.
For these reasons, in the Internet we ususally do not connect to each other directly, but we have to communicate passing every message to a mutual public service (such as facebook, gmail, skype, ...) which has the resources to pay for a public address and domain registration.
Once you are connected in Netsukuku, you can at no cost register one or more hostnames for your computer and host any service you like. Your service might very well be attractive to users located near to you, because they will feel a very fast response. More on this here.