Custom widgets are design elements which add some level of inter-activeness to your website, over & above the normal contact forms.
Sometimes they are simple modules, such as a pricing calculator or Opinion poll. Other-times they can be complex add-ons, such as appointment booking or customer surveys.
We generally limit the amount of custom widgets we include in our website designs as they make sites overwhelming for visitors, detracting from the website purpose. Further, interactive elements require a lot of support from the website owners and, if not maintained, can do more damage to the website than good.
Do you trust a site that has interactive content which hasn't been updated in ages?
So to keep things simple & focused, when we design our websites, we identify the custom widgets which suit our clients needs.