If your website is built by using wordpress then it requires at least one update in a month. It could be WordPress core, plugin or a theme update if you have used a premium third party theme.
Updates can be related to new features, performance or could be a security loophole/normal bug fixes as well. These all fall under Website Maintenance.
Website support is a change needed to your website that could be related to its aesthetic, adding plugin, new small functionality or could be even as small as adding a banner or an event to your website.
You need website support and maintenance services to take care of the above things.