I'm a relatively new player to the D&D scene. I'm creating a human ranger and was puzzled at the logistics of human traits, and I can't seem to find the answer anywhere, although I might just be bad at researching.

On D&D Beyond, when looking at the human race, under "Human Traits" it gives a list of Marks and Houses, such as Mark of Handling Human, followed by House Vadalis, then Mark of Making Human, followed by House Cannith, so on and so forth. And then at the end of the list is "Variant Human". With this context in mind I have 3 questions.

1. Are these Marks and Houses canon? As someone who has never really played, I have no clue if these are used regularly.




2. Do the Marks that precede the house listed relate to each other? e.g. is the Mark of Handling Human something given to you if you choose House Vadalis?




3. If you choose Variant Human, I understand that you forfeit the +1 to all stats in favor of the Level 1 feat and extra proficiency, on top of the +1 to two stats of your choice. But if I choose Variant (assuming Houses and Marks are canon), does this forfeit my choice of a house? Or do I get to pick a house on top of picking variant as a trait?

Marks are a variant for the Eberron setting

The Marks and Houses are from the Eberron setting availible for 5e in Wayfinder's Guide to Eberron. They are canon, but only relevant if you are playing in that setting (if you are your DM should have told you, if you are unsure just ask).
If you aren't playing in this setting you can turn off "Eberron content" under Sources in D&D Beyond's Character Builder. (You may want to turn off the others too, unless you know you are using them. Again ask your DM.)
If you want to read more on the Dragonmarks see the Unearthed Arcana article. The TL;DR is that they replace whatever other features humans would get (see below). The description of each mark says what it replaces. (The D&D Beyond version doesn't, for some bizzare reason.)

For non-Eberron settings there are two 'kinds' of humans: normal and variant. The normal get +1 to each ability score and that's it.¹ The variant is an option if your table is using the Feats-optional rule (ask your DM, chances are you do). If you use variant you get a few ability scores (+1 to two), some skills and a Feat of your choice (which may include a +1 to an ability score).

1: This isn't bad, but it might be underwhelming to some players.

The Houses and Marks described on the D&D Beyond page for humans are specifically from the Eberron campaign setting, described in the Wayfinder's Guide to Eberron handbook. The information about the Houses and the Marks is relevant to the world of Eberron, but they're not part of other campaign settings - unless, of course, your DM decides to incorporate them. If you're not playing a game in Eberron, you should probably ignore them.

Unfortunately the information on D&D Beyond isn't always helpfully organised in such a way that makes it clear what's what. You might find it more helpful to look at the race pages specifically sourced from the Basic Rules or the Player's Handbook, rather than the aggregation page you were looking at originally.

If you are playing in Eberron, the marks described are known as Dragonmarks, and they are associated with specific noble houses in the setting, so a character who has such a mark almost always belongs to the associated House. For a human, the traits associated with having the Dragonmark replace the normal human traits - as far as character generation mechanics are concerned, it's basically a different race. As the Wayfinder's Guide to Eberron says:

For humans and half-orcs, a dragonmark is a variant race that replaces normal traits associated with those races.

The Variant Human, if your DM is allowing it, is similarly basically another race that replaces the normal human ability scores bonus:

If your campaign uses the optional feat rules from chapter 6, your Dungeon Master might allow these variant traits, all of which replace the human’s Ability Score Increase trait.

You can't combine the variant human and Dragonmarked options - both of them are alternatives to the normal human racial traits. You're either a human with the normal human feature of having +1 to all ability scores, a variant human, or a Dragonmarked human.