There is milled wood and all the rest
Lumber from a mill is what is most often used for furniture and cabinets. All the other lumber has had a previous life.
Recycled, re-purposed and reclaimed are similalr but different in some aspects. Shipping pallets are one of the most common sources of recycled wood. There are shipping crates made of much larger and longer sections, actually huge timbers. Repurposed wood is used without changing it's surface, "as is". That would be barnwood or headboards from old furniture and the like. Reclaimed might be the sunken Cypress logs from the Southern swamps. Lumber milled from "picked" logs out of the firewood pile, as I have done with great results. Spalted wood from logs that have fallen along side the road is another source I have used.
You can make beautiful projects with all the above and even add new lumber to the mix with good results. Beauty is in the eye of the beholder and what works well for one, is not like by another. :frown2: My collection does not include pallet wood, but only because I have many other sources. I like it all. :smile3:
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)