I have created Collections that contain the photos from the Locations and Subjects I wish to display on my website. I simply drag the photos into the appropriate Collection.
The Adobe Photography Plan subscription provides the ability to "sync" these Collections to the Adobe Cloud. Using Lightroom, I tailor the appearance of the web page and use the created link (i.e., web address) to direct my site visitor to the appropriate page.
In the future, if I make changes to the content of one of these pages in Lightroom Classic (add photo, delete photo, or edit photo), these changes are automatically reflected on the web page.
Smart Collections
Collections, as described above, don't do much other than provide a place for you to collect some photos. Adobe Lightroom Classic has another type of Collection... a Smart Collection.
Smart Collections gather photos for you automatically based on rules that you create. If you have ever used a computer spreadsheet program, you are already familiar with the concept of Smart Collections. The "formulae" that you would enter into a spreadsheet cell is analogous to the "rules" that you create for a Smart Collection.
How might one use Smart Collections?
Note
Just like your photos are not "contained" within the Lightroom Classic catalog, your Collections and Smart Collections do not "contain" your photos only pointers to those photos.