Packet radio in the context of amateur radio has historically revolved around the use of the AX.25 protocol transmitted via FSK or AFSK at 300 to 9600 baud over FM or SSB. Most commonly, Bell 103 300Bd is used on HF over SSB and Bell 202 1200Bd has been used over VHF and UHF links. Links above 2400Bd require special hardware considerations and generally therefore aren’t as commonly used. Today we have software based modems to encode and decode enabling radically greater performance as well as the introduction of protocols such as FX.25 and IL2P which add a layer of FEC. The most popular use of AX.25 and packet radio today is APRS.
In the most basic of terms, packet radio allows us to interface our radios with computer applications much like bluetooth or WiFi but over greater distances at the cost of lower bandwidth. It's safe to say that the general SNR for your link budget is going to be similar to voice whether it be over FM or SSB. You can expect to find keyboard-to-keyboard chats, multiuser group chats, mailboxes, and bulletin board systems on packet radio frequencies. FARPN intends to push the boundary of what kinds of experiences are associated with packet radio.
The requirements for nodes and clients are going to differ but generally these three things are required:
Head over to Getting Connected for next steps on joining the network.