Guild Wars 2

What do these world events do exactly? And how do I participate in them?

They don’t show up anywhere on the map, just only show up at the top right corner with no description on what there is to be done really. But if you put your cursor over it, it states World Event.

Anyone have any information on them?

World events are basicly a chain of dynamic group events. with more oows and aaahs in the end battle. To identify them there is always a Dynamic event text active in the area.
on certain times of the day (mostly every three hours, but not always) the text changes for those in the area (roughly), if you go further to the center you will also get a message of a dynamic event. participate and you get an update, and another update till you are fighting the final world boss.

Take for example the secrets in the swamp event in the godlost swamp in Queensdale.
Most of the time you get the message:
‘The swamp lies dormant.’

This is the sign there is currently nothing going on.
sometimes you might see the message:
‘Underworld forces have been spotted outside the swamp’
This means one or all of the following Dynamic events are active in the area’s around the swamp:
Drive back Underworld creatures by destroying portals in the Heartwoods. (10)
Drive back Underworld creatures by destroying portals in the monastery. (11)
Drive back Underworld creatures by destroying portals in Taminn Foothills. (14)

If all three are completed the message will change to:
‘There is a disturbance in the heart of Godslost Swamp.’
If this one pops up, make sure you get to the center of the swamp cause it is bout to start.

When done it will change to:
‘The beast has been awakened!’ This means the gigantic world boss is up and you need to destroy it.

It takes however a bit of luck and timing to meet a world event. My guildleader just had his third one today, but only cause I told him on teamspeak it was happening and he traveled there quickly.