Guide to PvE

I was in wiki again and came across this page Guide to PvE

This sums it up nicely

PvE (Player versus Environment) is where most Guild Wars players will start their career. It is the perfect place to learn about the game and the concepts used in it, but it also has a rising difficulty curve: What starts out very easy will quickly become very demanding.

this is how a TEAM should be formed…

4 party members	6 party members	8 party members	12 party members
1 frontline 2 midline 1 backline	1-3 frontline 2-4 midline 1-2 backline	2-4 frontline 2-4 midline 2 backline	2-4 frontline 4-8 midline 2-4 backline

In almost every PvE situation, you will play together with others – be they henchmen, heroes or other humans. It is important to consider the composition of the team before heading out to slay enemies.