Watts or kilowatts (kW), and kilowatt-hours are all you need to know at the beginning.
Kilowatt-hours, kWh, is the size of the battery. In short, you don’t want anything less than 60 kWh. You can make a case for 40 kWh, but for nearly all North Americans, 60 kWh is the minimum battery size that’s practical in 2019.
kW is the size of the motor and in the mid-price range they’re all the same or nearly so. Most people can safely ignore this. kW is also the rate at which the car charges at fast chargers. Again, the difference isn’t significant in 2019, so you can ignore this too.
However, kWh–that’s important!