sudo 66-intree -zg
is the most descriptive of the structure of trees and services. Without sudo it will show you the user level trees and services, which is commonly found in the live obarun image and most wm/desktop installations is one tree with 3 services.
Look at the wiki page, there is a 66 intro document which shows you the most basic of commands and operations you need to know.
Other than boot tree as defined in /etc/66/init.conf and configuring the boot module, you should never enable any services on tree boot. With boot tree alone and a correct boot module configuration the system boots, it provides you an x amount of tty (consoles) and the tty12 emergency console. You can log in and work on things at this point. If you change the name in init.conf for TREE=tsoutsou then that will be the first tree that will be used for booting the system. 66-tree -n tsoutsou && 66-enable -t tsoutsou -F boot@ einstein && reboot
This in most cases will produce a functional system.
Names don't matter, you can call your trees one two three four ...
# 66-tree -nE one
# 66-tree -nE -S one two
# 66-tree -nE -S two three
# 66-tree -ncE -S three four
this sequence creates four trees, each starting after the other, if you have a reason to have a tree start after another. A common reason is a set of services requiring network to be already active, like a file server or mounting network drives, which may produce a series of errors if network is not yet available. But activating a service configuring the network doesn't always produce a functional network connection, especially if the ethernet cable in the back is just dangling free at eithe end :)
# 66-enable -t three -S ntpd
Starts and enables for the future a time server service in tree three.
You will find around the forum mention of tree root, which was the original 1st tree after boot since the very first edition of 66. The name root is used as contrast to user trees. No importance in the names used as long as it makes sense to you why you picked them. For example I use a tree named "net" to enable my networking service, dhclient@ eth0 usually. If all of a sudden I need wifi then I use tree "net" to enable them.
Keep asking, it is free :)