TRAITSIn their simplest iteration Traits are simple thematic, PC-specific descriptors. Your PC is really tall, ugly, attractive, good at cards, knows her way around a bar fight, grew up a beggar, grew up wealthy, grew up in such and such backwater. Whatever.
They're subject to GM review and approval, but I generally worry about (a) someone trying to
Everyone gets to make up as many Traits as they want, but their PC can only roll with two Traits in a session. They can swap out between session, but they have to come to the table with their new Traits in hand.
HOW THEY'RE USEDThe PC is trying to do something in the game other than trying to hit something. Ride a linnorn, smooth talk a lich, shake down a wyvern, that kind of thing. The PC's player explains how their PC is trying to do what they're trying to do. And also, hey, because they've got this Trait (good with animals, good at reading reactions, embalmer, remarkably strong, whatever), shouldn't maybe the PC be kind of better at this than they would have been otherwise? It's the player's job to tell me why and how the Trait is applicable, but unless it seems like a clever application or a very obvious application, I probably won't honor it.
If I think it makes sense, you get a bonus point in the preferred direction on whatever roll you have to make. That's a bonus point from the Trait alone, over and above whatever points (one or two) you may have got for clever planning (and if you planned really poorly and lose points on your roll, you do not get a bonus point from your Trait).
AN ASIDETraits tell me and everyone else at the table something about the PC, so there's that element of player-PC-setting interaction that is interesting, and I've found that this helps getting new/infrequent players into the setting/game /PC a bit more quickly. It especially seems to help encourage the shy players, which is nice, but it's hardly the only way of doing that.
RATIONALEI figure Skills, Feats, Talents, and Professions are all ways for the Player to signal to the GM, "hey my PC is this/likes to do this too." They're in addition to whatever is involved with the PC's Class and they expand the character beyond the fundamental mechanics associated with their race and class.
I figure Traits can scratch that itch. (and yes, Skills, Feats, Talents and Professions do other things too)
I also think Traits are are just a formalization of what players do anyway, so they shouldn't muddy or complicate the enjoyably simple dynamic of OD&D play. (In fact, once everyone gets how they work, they ultimately make things go more quickly because they limit the number of things the player can try to use to convince me that something should work).
picture is by Tatsumi.