yeah, I don't think it is a perfect analogy for Meltdown, I'll try one, someone correct me if I'm misunderstanding Meltdown.

Let's say you want to know if your boss is away on vacation next week so you call their admin and say "you need to double-check my contact info if the boss is going to be out next week". They load up the boss' calendar to check and based on his presence next week then load up your info. Only once done, do they take the time to remember the boss didn't want you to know wether they are in or out. So you hear back, "sorry, can't tell you that, but you follow up with "OK, well can you still double check that my phone number is..."

If they respond quickly with a yes, then your file is still on their screen and the boss is in fact out next week. If there is a short pause while they look it up, then the opposite.

A timing attack is one type of side channel attack. These types of timing attacks can also be used against poor/unsuitable crypto functions, or even some processes involving general computation e.g. If it takes longer to reject input A than input B, you can reason that input A is closer to the answer (similar to someone reading a paragraph until they reach the first error).

Other side-channel attacks can come in the form of analysing network data, power-consumption (CPUs use more power when they are "busier")... even noise (listen for when the fans start spinning up).

Yes, this is a general explanation of side channel attacks against some kind of caching. The more specific example tries to be closer to the type of situation that happens in Spectre, but it is not a direct analogy.