Internet Protocol Security (IPSec) is a set of protocols that provides security for Internet Protocol using advanced cryptography. IPSec is similar to a Secure Socket Layer (SSL), except that SSLs connections are typically used by web browsers, while IPSec tunnels (usually) require a client application installation. Furthermore, IPSec tunnels can access both web and non-web applications, whereas SSL requires workarounds for non-web access such as file sharing. IPSec was designed to serve the IP Protocol, so it is mainly used to support Virtual Private Networks (VPN) over the Internet.
Additional Reading: VPN protocols: What Are They And Which Should I Use?
What does this mean for a SMB?
In all cases, never rely solely on a password authenticated VPN. The minimum security practice is to enable two-factor authentication on your VPN. There are too many passwords breached online that could be used by hackers to breach your VPN network. Always pair VPN access with a second factor.