<h3>buffer function</h3>
Returns a geometry that represents all points whose distance from this geometry is less than or equal to distance. Calculations are in the Spatial Reference System of this Geometry. 

<h4>Syntax</h4>
<pre>buffer(a, b)</pre>

<h4>Arguments</h4>
a &rarr; geometry
b &rarr; distance for the buffer

<h4>Example</h4>
<pre> buffer($geometry, 10.5 ) &rarr; returns a polygon</pre>