What's the difference between car speakers and home speakers? Can car speaker drivers be used at home?

The difference is as mentioned in the impedance - car speakers are 4 Ohms and normally, home speakers are 8 ohms. As for the second part of the question, yes it can be done; Provided - a) you wire the speakers so that their effective impedance becomes 8 ohms. b) You have a home amplifier that can drive 4 ohms speakers. The reason is that a lesser impedance speaker (car speaker for instance) will draw more current from the amp causing overheating and blow out of the amp if it cannot handle the extra amperage required to drive the speakers. So you need to ensure that the speaker impedance matches your amp rating. In case you would still like to use car speakers with your home amplifier, I would suggest connecting a pair of car speakers in series for each channel so that their effective impedance is 8 ohms (4 ohm + 4 ohm). House this in good quality wood/particle board enclosures lined with sound absorbing material and you will find that you can put together a high quality speaker system as a DIY project. In such a setup, by using a pair of 4 ohm tweeter and a 4 ohm two-way speaker connected in series, you can make a speaker with better frequency response than the normal ones you buy. One more thing to remember would be that most car speakers do not come with magnetic shielding, so will have to be placed away from your tv in a home set up.

Impedance. Car speakers are rated 4 ohms. Home speakers are 8 ohms. It is easier to overdrive your car speakers with your home amplifier and blow them.

Car amplifiers generally use lower voltage and higher current than home systems and therefore use lower impedance speakers to allow suffiently high electricity (current) flow. Half the voltage means half the impedance for the same amount of current to form a given magnetic field in the speaker coil. Nominal impedance for car speakers of the set of speaker elements within such a "speaker," to the amplifier is 4 ohms, or only half of the regular 8 ohms. If your amplifier can handle the higher current (roughly double that of home system) then you will get somewhat more delivered power to the car speakers. Most amps describe ratings for different loads. Read the ratings of the amp. Many state a power (often about 50% higher) output for 4 ohms as well as 8 ohms. If an amplifer can take 4 ohms (or even 2 ohms) it should provide a (generally much higher) power output rating for that load. If it doesnt, then I would only use the home amp for regular 8 ohm speakers only. Car "speakers" are generally higher quality and higher fidelity for the same size, compared to home speakers. Also, I would not put 2 or 4 ohm speakers in series to sum up to 8 ohms, since the quality of impedance (proportion of inductive (coil) reactance vs. capacitive reactance (both of which change with frequency) vs resistance (DC) reactance) will differ between speakers and also change with audio frequency. The sound quality likely will suffer when doing this.