Hey there!
In this fraction, we can imagine a circle, divided into four parts. One half of the circle with two parts, and the other half with another two. Shading in one is 1/4, and shading another would be 2/4. When we imagine this, we see that half the circle is filled, therefore it's not in simplest form. If we divide the top by 2 and bottom by two, we get the same answer as we've seen in our picture. It's equal to one half.
Hope this helps!