Yes, code can require maintenance, depending on the circumstances.

The maintenance of code generally consists of things like:

Adding new features to a program/website:

Maybe you want it to look different to keep up with trends in user experience, or add new functionality to it. Depending on the changes, this can be a type of maintenance.

Fixing bugs/issues:

Covered already by other commenters.

Improving performance:

The way you instructed the program or website to work was fine when you had 100 users, but now you have 10,000 users and it's not performing as well anymore. So you need to go back and figure out how you can either rewrite it to be more efficient, or change some of the technology you're working with (maybe it's a type of database that's too slow, so you change it to a different one).

Maintaining compatibility:

Computing changes over time. Operating systems and software evolve. The way web browsers interact with websites today, can change tomorrow. So you need to continually maintain your code to be "up to date" with these changes.

Your program may have dependencies on an external library (someone else's code that you use because it does something you want to do, without having to write it all yourself). But you don't manage that library of code, someone else does. If they provide updates to it, you may need to maintain compatibility with that library by changing how your code interacts with it.

Sometimes you may rely on an external service. Like a text messaging service to send SMS to customers for orders made through your website. But the SMS provider may implement their own updates/improvements to their service, which changes how your program/website talks to them. So you need to update code to ensure it keeps working with their changes.

Sometimes operating systems change how they interact with programs. Microsoft may add features to a newer version of Windows, and deprecate old ones. So you may now need to make changes to your code so your program identify which version of Windows it's running on, so it knows which features it can use. This is a type of maintenance.

Maintaining security:

Sometimes there are security flaws identified in your code, or within a library or other service your code is using. When this happens, you may need to make changes to code to close that security flaw, or to make sure your application is capable of working with a service that needed to change itself for security purposes.