What this coin looks like (obverse, reverse, mint mark location, special features, etc.): One major variety is the 1820 Capped Bust Half Dollar which features a square base on the number "2" in the date. The bottom of the "2" is flat and square opposed to the other variety that has a curved and curled base. This variety features a larger date as well.
The difference between the 1820 Square Base 2 vs Curl Base 2 is depicted below in the example comparison image:
The 1820 Square base "2" variety also has two sub-varieties as well. This variety features no knob on the upper tip of the "2" - but instead curls around without the knob at the end. The other variety does have a knob and doesn't curl around and up. The difference between the knob 2 vs no knob 2 is depicted below in the example image:
Lastly - the difference between the small date vs large date is also depicted below:
Coin value chart: Typical coin prices, values and worth in USD based on grade/condition