This is for employee stock purchase plan. You do not have to report it on your tax return now unless you sold the stock-- this will be your basis (how much you paid) when you sell the stock so it is a good idea to keep this until then and make sure it matches what you have on your broker statements (For the Turbo Tax entry use Other not on the list)
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Box 14 is, in the main, a "memo" field where employers tell you something about your W-2. In this case they are reporting the compensation created by the SALE of stock acquired via an ISO or an ESPP. That compensation is included in Box 1 of your W-2.
Since Box 14 is generally "memo" information, entering that information using the W-2 interview, or not, typically does not affect your taxes.
You have a stock sale to report, clearly. You use this information to help you determine the correct basis to use for the sale, an amount that almost certainly is not correctly reported to your on your 1099-B. Brokers are only required to report your "out of pocket" cost here, not the correct cost which is the sum of your out of pocket cost and the compensation created by the sale.
If you know what your basis is for the sale you can enter the 1099-B exactly as it reads and then click the blue "I'll enter additional info on my own" button. On the next page enter the correct basis in the "Corrected cost basis" box. If you are not sure of your basis then select "Guide me step by step" and select the proper interview, either ESPP or ISO.