Any device that runs software may need regular updates.
This could include: your desktop, laptops, tablets and phones, your firewalls, hubs, switches and routers, other hardware, smart devices and no doubt more, depending on your industry.
It includes firmware, operating systems and software applications (commercial off-the-shelf, or in-house), your website and web applications. Think about everything on your network, and services provided to you through the cloud.
And, depending on your agreement with your provider, you may also be responsible for updating the server software that your email, cloud applications and websites run on, and the security software that protects it, and so on.
The first step in patch management is to know what you have that might need updates. It will probably be a longer list than you anticipate.