[inimino]

An encyclopedia tells you what quantum mechanics is. You can use that knowledge the next time you are at a party and someone wants to talk about a cat in a box or the double slit experiment. You cannot use that knowledge to teach an undergrad course on QM that involves any math, or even to design a meaningful experiment in the field.

If you want to know what functional programming is to casually mention it at parties, you can easily find an explanation at that level. If you want to determine whether it is worth learning and using, and what it is good for, you're not going to get that without some experience and some investment of effort.