Pixel pitch, resolution and pixel density all these terms are interrelated. Let’s see one by one.
Pixel Pitch:
Pixel to pixel distance, or gap between two pixels (often refers to dots or lamp beads). It is typically measured in millimetres and is a key factor in determining the display's resolution image clarity.
Resolution:
Resolution refers to the total number of pixels arranged horizontally and vertically on a display.

For Example:
 if a single P5 outdoor SMD module contains 64 pixels across its width and 32 pixels along its height, its resolution is defined as 64 × 32.
*GKGD SMD modules standard dimensions (320 × 160 mm) except P3.91 i-e (500 × 500 mm).
Pixel Density:
If we continue above example pixel density indicates the total number of pixels present within one SMD module i-e P5 outdoor SMD module, multiplying the width and height pixels (64 × 32) gives a total of 2,048 pixels. This value represents the module’s pixel density, which plays a crucial role in determining image clarity.

Understand this after comparing below table of indoor and outdoor SMD Models

Smaller pixel pitch results in higher pixel density
A smaller pixel pitch means that the pixels are packed more closely together, which increases pixel density and resolution results in sharper, more detailed images.

Higher pixel pitch results in lower pixel density
A larger pixel pitch indicates that the pixels are spaced farther apart, which reduces both pixel density and resolution, leading to images that appear less sharp and less detailed.

GKGD Indoor SMD models pixel pitch, resolution and pixel density.
You can get idea which model is suitable for you.
*The letter "P" in model name represents the Pixel Pitch of the display.
*Standard size of all indoor modules (320 × 160 mm) except P3.91 i-e (500 × 500 mm).
* The terms dot, pixel, and lamp bead all refer to the same basic unit of a display.

GKGD outdoor SMD models pixel pitch, resolution and pixel density.
You can get idea which model is suitable for you.
*The letter "P" in model name represents the Pixel Pitch of the display.
*Standard size of all indoor modules (320 × 160 mm) except P3.91 i-e (500 × 500 mm).
* The terms dot, pixel, and lamp bead all refer to the same basic unit of a display.
*Px stands for “Pixels”
*P3.91 modules mostly use in rental SMD display.