00:00 What are Samples#
1 Sample means 1 calculation of the light in your scene. 100 Samples means 100 calculations.
The more Samples you have the more accurate, beautiful, smooth, refined your lighting will be.
Graininess/Noise is the result of low Samples.
A really long Render Time that makes you wait all night is the result of high Samples.
Use Slots in the Image Editor to Compare a Low Sample Render in Slot 1 with a High Sample Render in Slot 2.
Until you start comparing the effects of different Sample amounts, you'll never understand them.
01:48 Animated Noise#
Your animations will have some noise. It's unavoidable.
The noise will look better if it's Animated rather than Static.
Go Render Output Tab->Sampling->Advanced->Seed and enable the Clock Icon to get Animated Noise.
View Layer Tab
Scroll to the Bottom and check the Denoising checkbox.
Denoising is less accurate than cranking up a higher Sample count, but it is much much faster than rendering at a high Sample Count.