If you find a path, then you´re related, if the path are blue all the way from you to that profile, you share a common ancestor, if there are different colours, you don't share a common ancestor, (exception; if it displays the shortest way, you could still share a common ancenstor, but the lines goes thru one or several cousins marriages and that path is just the shortest one, thus displayed), if you don't find any path at all, you´re not proven related, meaning, you could be related, but there are no connection to establish a searchable path.
I do not use the word "relative" to refer to folks that are only connected to me thru multiple marriages. If the path shows multiple colors, I take that to mean we are connected, but not related. (Exception: if it is just at one end or the other, for example, the spouse of my mother's brother I consider my relative - an aunt - not the wife of my uncle).
I am surprised to see Ulf considers folks connected thru multiple marriages to be relatives - apparently the word means different things to different folks.
Lois, the affinity is the opposite to bloodband related people, which appears with a different color than blue here on Geni, they are not related by blood (or the relationship has a longer path so it doesn't show that, and remember, with or without a path, we are still (to some people's disgust) all related due to the fact that there is only one human species with common origin), but are relatives in a broader sense, and Swedes make a difference between people belonging on that part versus people belonging to their side by blood, but this is something that various in different cultures, where some might count them in as relatives just as much so don't be surprised over some people who actually does that.
Smart Matches are to Trees not on Genii. If you find it interesting and/or useful to see those matches, then I guess it is.
Tree Matches are to other Profiles on Geni. Be very careful it truly is a match before confirming*, since it can mess things up a lot if it wasn't - but confirming a Tree Match is how you would probably get attached to the World Tree, since confirming Tree Matches results in the two profiles being merged into one (or if the other is Private, in a request to merge being sent, which might be accepted at any time ).
-- -- *but if you do goof - Curators can now undo a merge, and they can help untangle if that is needed, as well (Curators can also complete a merge you requested, if nothing ever happens in response to your request). [If you end up needing a Curator's help to undo - or to do - a merge -- post in this discussion: https://www.geni.com/discussions/178003 ]