If you are considering changing or updating your website, there are 3 options which are available to you; refresh, redesign or rebuild.
A website refresh essentially is any update that doesn't change the overall functionality and code of your site. This could be something as simple as changing a few colors and adding your new logo, updating fonts in the header or menus, perhaps replacing older images and content
A website redesign on the other hand is a little more drastic, like an entire new base theme or template.
While a website rebuild involves creating a completely new website from scratch. If your website were a house, a rebuild would mean we would tear down the old house and build a new one in its place, perhaps keeping the plumbing and electrical hookups. We might reuse some elements from your old site, importing things such as product data and images, or blog posts for example, but the rebuild essentially involves creating a brand new design, website structure, and using a new or updated underlying CMS.
We generally recommend that you do a full website rebuild every 5 years (due to technological advancements), a redign every 2-3 years, and a refresh every year after getting your new website.