A password is a lock, and like any single lock it can be picked. Passwords get guessed, reused across sites and then leaked when one of those sites is breached, captured by a convincing fake login page, or simply worked out by someone who knows a little about you. For the accounts a business truly depends on - its email, its money, its customer records, the places where real damage could be done - relying on a password as the only barrier means that the moment that one secret is compromised, whoever has it is in. That is a lot of trust to place in a single string of characters that has more ways to escape than most people realise.
Two-factor authentication - sometimes called two-step verification - closes that gap by requiring a second, independent proof of identity on top of the password. The idea is simple: to get in, you need something you know (the password) and something you have (typically your phone). In practice that second step is usually a code from an authenticator app, a prompt you approve on your phone, or a physical security key. The security comes from the fact that the two factors are separate: a criminal on the other side of the world who has stolen or guessed your password still does not have your phone in their hand, and so the stolen password alone gets them nowhere. It turns a single lock into a lock plus a deadbolt that only you can reach.
It is worth being deliberate about where you turn it on first, because not every account carries the same risk. Start with the ones that would hurt most if taken over: your main business email (which, as it happens, is often the key to resetting everything else), anything involving money or banking, the systems holding customer data, and the logins for your website and important online tools. Enabling it is usually a quick setting found under the security or account section, and the small daily friction - entering a code or tapping approve when you log in - is minor next to what it prevents. Where you get a choice of method, an authenticator app or a physical key is generally more robust than a code sent by text message, though any second factor is a large improvement on none.
One habit makes two-factor a protection rather than a lockout risk: keep your recovery options in order. When you set it up, most services offer backup or recovery codes - save those somewhere safe and offline, so that if you lose or replace your phone you can still get in. Think ahead about how you would recover access if the device holding your codes were lost, and for a business it is wise to make sure critical accounts are not tied to a single person's phone with no fallback. Set up thoughtfully, two-factor authentication is one of the highest-value security steps a small business can take for the least effort - a few minutes per account, in exchange for making a stolen password almost useless to the person who stole it.