I need a good definition of "Capital Gains Tax"..

[IreneS]

Capital gains tax is a tax imposed on profit from the sale of property or an investment. The most common capital gains are realized from the sale of stocks, bonds, and property.

If you sold stock at a profit, that profit is not just added to the rest of your income for tax purposes.  The capital gain is taxed as a separate category, and usually at a lower rate than the rest of your income (if its a long-term gain).

In 2018 the capital gains tax rates are:

• 0%, 15% or 20% for most assets held for more than a year (long term gains); or
  
• 10%, 12%, 22%, 24%, 32%, 35% or 37% for assets held for less than a year (short-term).  The rates  correspond to ordinary income tax brackets.

For more information, please see this FAQ:

https://ttlc.intuit.com/replies/3301738