Commonly when we create site collection, we need to sign in SharePoint Admin center. Some sites are created by Microsoft Teams, as every new Team gets a SharePoint site because the team has created an Office 365 Group. When an Office 365 Group is created, a related team site will be created automatically.
You could also create site collections using powershell, for example:
#Connect to SharePoint Online Connect-SPOService -url "https://crescent-admin.sharepoint.com" -Credential (Get-credential) #Create a modern team site New-SPOSite -Url "https://crescent.sharepoint.com/sites/Purchase" -Owner "Salaudeen@Crescent.com" -StorageQuota 2048 -Title "Purchase Team Site" -Template "STS#3"
For more information, you could refer to:
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