One of the big promises of the Xbox Series S and Series X is higher framerates in games.
It might even be one of the reasons you wanted one for Christmas!
While the previous generation often reduced frame-rate down to 30 frames-per-second to maintain graphical fidelity, many of the games on Series S and X are targeting 60 frames-per-second as a minimum.
While many games are aiming for 120 FPS, that'll require your TV or monitor to offer 120Hz.
Here's how to set it up.
Xbox Series S/X: How To Get 120Hz
To get to the page you need, you'll need to open the Settings app.
This new power is why the console has to be so well ventilated! Source: Xbox
You can find this either in your "My Games and Apps" folder, in the apps category, or by opening the Guide (press the Xbox button) and navigating to "Profile and System" and selecting "Settings".
Once in settings, head to "TV and Display Options", and from there you'll be able to select your resolution.
You'll also find a "Video Modes" option, which will let you select 120Hz – but will only work if your TV supports HDMI 2.1.
In my case, my Series X is connected to an Ultrawide monitor with 144Hz refresh rate, but it can't output anything higher than 60FPS because the monitor doesn't support HDMI 2.1.
The bad news is that you'll need a fairly new TV or monitor.
No one console should have all that power. Source: Xbox
As for 1440p screens (the resolution that Xbox Series S caps out at), the first monitors of that type with HDMI 2.1 are launching soon – but are expected to be pretty expensive.
Still, the jump from 30 FPS to 60 FPS is arguably more noticeable than anything higher, so it might be that you'll be quite satisfied with that.