Yes, you can have multiple sites defined within one instance of Episerver. CMS supports it by default.

To configure websites, go to CMS Admin panel (/episerver) -> CMS -> Admin -> Config tab/ Manage websites. There you can have multiple websites configured, each one with different start page.

As Kpkozak said, there's there's multisite features built in. See https://webhelp.episerver.com/latest/en/cms-admin/managing-websites.htm 

Thank you for the feedback to both of you. Just looked at the documentation. Looks good!

Quick question regarding this topic. If we go ahead and set up a subsite, can we assign a user role or group that is allowed to only edit the subsite but not the main site and assign users to this role/group?

Yes, you can define a group and then assign that group to the subsite with edit access right. More information can be found here Access rights (optimizely.com)

Hello again, thank you for the feedback. Just another question as I gather all the info. The subsite will have it's own Startpage if I understood it correctly. Does that mean we can also add a new Google Tag Manager tag for this subsite into the Startpage? i.e. will we be able to track the subsite independently in GTM using the out of the box EpiServer CMS functionality for subsites?

It depends on you how you'd model this, but this is definitely achievable. One of possible solutions would be to have GTM container Id setting as property on start page, and then resolving it based on the homepage. You can have separate containers then for each site.

Thank you for all the feedback. I assumed that the subsite will allow me to add a newly generated Google Tag Manager tag either through the Admin config, or by adding it to the Analytics property on the relevant Startpage?

Hi again, so we have opted to create a subdomain for the subsite. This CNAME was created for us, but when I try to load it in the browser the name does not resolve anywhere.

I tried setting up the addition website in the EpiServer CMS Config > Manage Websites section but the error persists and I am unable to view the Startpage (even in the backend) of the subsite.

Is there any guidance on what settings the CNAME needs to have? Does it need to point to our existing website servers IP? Or what is required here (a-record or c-record)?

Are you self-hosting this site, or is DXP?
If it is DXP, the support can (must) help you setting up the domain.

Thank you for the info, it's DXP am in touch with Support. I wasn't aware that Support needs to be involved as the documentation makes it sound like you just click and go. 

So the additional sub site has been set up with the help of Support. However I am unable to create any pages under the new section, neither am I able to edit the new Start Page in "all properties" mode. Any tips on what the cause could be? As a precaution I tried restarting the web app, but that did not help resolve the issue.