To expand on what Defibulator said:
After pressing enter, you can select a variety of chats such as private chats, guild chat, party chat, zone chat, world chat (world chat costs megaphones which you can get from in game events or from buying them with diamonds [in game currency bought with rl money]). Guild chat is /g[Hit Spacebar Here] , party chat is /p[Hit Spacebar Here] , zone is /z , world is /y , and private chats are listed based on their number when you join them (1-9) and are called the same way as the others. To respond to a PM or whisper, you press r, and pressing Ctrl+r allows you to whisper a player you previously whispered. To directly whisper a player that you know the name of, you can type /w [Player's Name Here]. To join the main Osha talk channel between many guilds and people, type [/join Trade] (no brackets), then hit enter.
A character is bound to a server, however, you can create characters on each server using the same account.
And it would help to have a clickable link for RoM-Welten's info, though players on forums can help that as well. (I personally suck at planting, so... yea. lol)
http://www.rom-welten.de/en/articles,id578,0,planting.html