The guard is one of the components (but beware, not necessary in 100% of knives on the market) of the knife construction placed between the blade and the handle (or unmistakably protruding part of the construction), whose function is purely safety. It serves to prevent you from cutting your hand and fingers on the knife.
The guard comes in various shapes, this is one of the more common ones on survival knives.
Is a knife safe even if it doesn't have a guard?
The usual problem for a user choosing an outdoor knife is that their ideal has a small (or even no) guard, and the customer is unsure if the knife would be a safe choice for them.
In such situations, it is naturally best to stop in person at the store and try the chosen knife directly in your hand and swing it in your hand according to the planned actions (like a quick draw from the armpit holster).
Alternatively, order two or three knives (everyone is different logically), try which one fits your hand best and return the rest.
However, there are also certain unique knives (especially in the kitchen or for certain very special work activities), which do not have a guard or perhaps a part of the blade serves as a guard (logically it must be blunt and have a width of at least a few cm).
Although some people don't use a knife guard as a matter of principle, their philosophy certainly shouldn't be standard among survivalists. Looking for (and god forbid using) a knife with an unprotected blade in the dark and half asleep is really unwise (and literally) for your fingers!
Here, the advice will be very simple - choose a sufficiently massive, reliable and strong guard from the view! Your safety comes first, so beware of all kinds of cheap knockoffs of brand name knives in the corner of a flea market…
In short, the more often you get your hands on a particular knife, the better protection you should expect from it.