MacBook Pro screen resolution confusion

I noticed something weird on my Mac:

The resolution in specs is 2560x1600 (13" MBP). In System Preferences, It says that the resolution "looks like 1440x900", but does not mention the actual resolution.

When I take a screenshot, the resolution is 2880x1800 (in the screenshot file's metadata)

The screenshot.app in CMD+Shift+4 mode shows a crossbow with coordinates, the coordinates say 1439, 899 when moved to the bottom-right corner.

And third-party apps (like OBS) show 1440x900 as the resolution.

Why is that happening and what's the "actual" resolution of my screen?

Edit output of system_profiler SPDisplaysDataType as requested by @ankii:

Graphics/Displays:

    Intel Iris Plus Graphics 650:

      Chipset Model: Intel Iris Plus Graphics 650
      Type: GPU
      Bus: Built-In
      VRAM (Dynamic, Max): 1536 MB
      Vendor: Intel
      Device ID: 0x5927
      Revision ID: 0x0006
      Metal: Supported, feature set macOS GPUFamily2 v1
      Displays:
        Color LCD:
          Display Type: Built-In Retina LCD
          Resolution: 2560 x 1600 Retina
          Framebuffer Depth: 24-Bit Color (ARGB8888)
          Main Display: Yes
          Mirror: Off
          Online: Yes
          Automatically Adjust Brightness: No
          Connection Type: Internal

Solution 1:

Many many OS X versions ago, Apple rolled out "Resolution Independent UI" in order to ensure that UI elements were rendered consistently regardless of the DPI of the display. Prior to this, all displays were assumed to operate at 72 pixels per inch (ppi). Prior to that, if you wanted the main Mac menu bar to be 3/8" high, you would simply multiply 3/8 by 72 to set how tall the element is.

Why do I bring this up? Because with this foundation in place, Apple rolled out retina displays with DPIs approaching 300 ppi. Your display is one of these and indeed has a Fixed dpi of 2560x1600 (per specs). The underlying resolution independence ensures that the UI elements display at a consistent size across resolutions, screen sizes, and pixel densities.

In summary, from my understanding:

• Your Screen's resolution is fixed at 2560x1600px (see note below)
• Your "virtual" resolution is set in displays preferences, and you have it set to "look like" 1440x900
• "Full Screen" screenshots (⌘-⇪-3) appear to capture in "native" display resolution. (see note below)
• "Marquee" screenshots (⌘-⇪-4) appear to capture in "virtual" display resolution.

note: The 2880x1800 resolution in your screenshot appears to be a 2x of your virtual resolution of 1440x900