Everything Under the Moon

I have read different books, and they mention the Summerland, where Celts believed you would go before reincarnation (is that correct?) But I can't seem to find much about the Summerland specifically. I may be looking in the wrong places. Could anyone clarify this?
Thanks!

Summerland is Wiccan not Celtic, I do believe.

You're right, for some reason I connected the two. I think I see Summerland more in my readings that are more for general. I am curious because it is mentioned but not explained. I guess because most of what I have started off with deals with just a general overview but doesn't go into explanation of after death with the Summerland.

Summerlands?

Tír na nÓg; "Land of the Young" or "Land of Youth" depicted as a paradise and supernatural realm of everlasting youth, beauty, health, abundance and joy. The inhabitants enjoy a life of eating, dancing and loving and they never have to deal with death or dying. Its inhabitants are the Tuatha Dé Danann. In the adventure and voyage tales, various Irish mythical heroes visit Tír na nÓg after a voyage or an invitation from one of its residents (The Voyage of Bran for example) . They reach it by entering ancient burial mounds or caves, or by going under water or across the sea.

Also...
Tír Tairngire; "Land of Promise/Promised Land"
Tír fo Thuinn ; "Land under the Wave".
Mag Mell; "Plain of Delight/Delightful Plain".
Ildathach; "Multicoloured place".
Emain Ablach; the Isle of Apple Trees
Annwn.
Fairyland.
Hy Brasil.
The Celtic Otherworld.

The Voyage of Bran

(Link) https://m.youtube.com/watch?v=AQ8xP_Z8q0E