A whitelist, or allowlist, is a list of programs, websites, or IP addresses that are trusted, whereas a blacklist is a list of such things that are not trusted. For example, some email spam blocking programs use whitelists to allow mail from specific email addresses or blacklists to block mail from specific email addresses.
When it comes to VPNs, whitelisting can mean a few different things. A business might whitelist the IP addresses of employee’s home routers so only authorized personnel can connect to the VPN and access the corporate network.
The split tunneling features in the VPNs recommended above give users the power to decide which apps or websites use the VPN’s encrypted connection and which use your default, unencrypted internet connection. Generally, whitelisted programs must go through the VPN and blacklisted programs are allowed to bypass it. If you need to bypass Microsoft Teams so that it doesn’t use the VPN, you would blacklist it. A VPN that only allowed whitelisting would be more cumbersome.
Some VPNs call whitelisting inverse split tunneling.