Use Animal Classification, and stuffed animals if you like
This strikes the right balance of fuzzy approachability with a feeling that this is serious “science stuff.” Use some cheap stuffed animals as props, if you like, and maybe use a PowerPoint presentation with frequent animal photos — people like animals, and most will “perk up” whenever they a good animal picture.
It helps that the biological classification system is a “real thing” and that most high school graduates will remember it a little.
The one caveat is occasionally you can run into a person whose world
view is challenged by discussing a subject related to evolution. You
can assure those individuals that you are “just talking about
The animal metaphor works best if you know a bit about Biology and the animal
classification system. If you really don’t remember your High School
bio, and forget the common attributes of mammals,
you might be better off using an example you can speak
In any case, avoid high-tech themes for your example. Most lay persons really don’t care about computer models or peripherals. These motifs will just reinforce notions your audience will probably already have, walking in, that this whole subject is “for techies only.”
Concepts to describe:
Classes and objects — The ideal of dog, vs individuals dogs.
Method and attributes — Dogs are furry. Dogs can bark.
Overrides — Not all dogs have hair.
Inheritence — Dogs are mammals. Dogs can generally do what mammals can do (method inheritance) have attributes that mammals have (attribute inheritance).
Abstract Classes — No actual animal is just a mammal.
Inheritence from a concrete class — Scottish deerhounds are dogs that have no bark method.
Composition — A dog or another animal can have a collar, but a collar isn’t part of the animal.
Slightly more advanced concepts
The above is as far as I’ve ever taken it with a first talk, but you can go on:
Association — A dog or a cat can have a collar. But the collar is also an independent object. You can give the dog away, but keep the collar.
Aggregation — A fish may belong to a school. If the school is swallowed by a whale, the school is destroyed, along with all the fish in it.
Inheritance Chains — Dog is a Mammal is a Vertibrate is an Animal is a life form. (And point out that computer systems can be this complex too.)
Involve your audience
These are all tough concepts, and you are probably going to get a lot of glassy stares if you don’t actively keep folks involved and talking.
For example, don’t list dog attributes and methods yourself, ask for input from the group. (People are hard-wired to be interested in animals, so that helps.)