Eid means festival and there are two main Eids in the Muslim calendar. Which is lunar, so the dates very from year to year.
This one marks the end of Ramadan, the month of daytime fasting. Very difficult this year as it fell at the time of longest days. There's a big feast evidently.
The other Eid falls in September this year and commemorates the biblical story of Abraham being told by God to sacrifice Isaac. He kills a sheep instead eventually. So the festival involves slaughtering a sheep.
Husband once went with a friend of ours who has a sheep farm to the sheep market at that time, and there were many Muslims bidding for the best animals.
Tanith - sorry no idea if non-Muslims can attend though, it would probably be ok.