You might have a collection of websites that you frequently want to visit.
To open a collection of your favorite bookmarks at once when you open Safari you can change the presences:
Safari > Preferences > General: “New windows open with “choose a tab folder”
If you are researching the web and want to collect the links to the pages only for the duration of the project, you can create a quick link to a website by dragging the small icon at the beginning of the URL and to the desktop or folder.
To open the collected bookmarks at once, select one or more links and double click on one of the selected links top open them as tabs in your favorite web browser.
You can close all the tabs with the keyboard shortcut:
"Command + Option + W"