I don't even understand this ohms thing
Ohms is a measurement of resistance or impedance to the flow of electricity. The lower the ohms rating, the lower the resistance or impedance. That makes it easier for the electricity to flow. However, that can be a dangerous thing for amplifiers, which have limits on what they can handle regarding the flow of electricity. The extreme is 0 ohms, which would be shorting out the output of the amplifier, which, in most cases, is something that can potentially damage an amplifier, though some have protection circuitry to prevent damage and will just shut down instead.
What this means in practical terms is this: You want the amplifier to be capable of handling the impedance of a particular speaker if you are going to use that speaker with that amplifier. If you have a speaker that has a minimum impedance of 8 ohms, than anything rated for 8 ohms should work with it (though if it is very low powered and the speakers are of low sensitivity, you may not get much volume). Beware, though, of "nominal" impedances, as some speaker companies essentially lie about this in order to make a sale even though the speaker is not suitable for use with an amplifier that can handle that impedance and no lower.
Here is an article with some more information:
https://en.wikipedia.org/wiki/Electrical_characteristics_of_dynamic_loudspeakers
There are standards for what "nominal impedance" means, as in that article, but, evidently, there is no legal definition of the expression, and many speaker companies give a number that is not even close to what the "nominal impedance" is in that article. In other words, they lie.
