Imposition of Federal Gift Tax
Gifts totaling more than the annual exemption amount ($15,000 in 2018 and 2019, $14,000 in 2017) to one person in one year are referred to as taxable gifts and generate a potential Gift Tax. It does not matter if you give one $15,000 gift or 15 gifts of $1,000 each, or one gift of $13,000 and a "birthday gift" of $2,000. Gifts of a "future interest", no matter what their value, also are considered a taxable gift. Unlimited gifts can be made to a spouse who is a US citizen.
If you go over the $15,000 per person per year amount, you have to file IRS Form 709, to report the gifts.
Taxable gifts generate a Gift Tax. But Gift Tax is not due until you give away over $11.4 million (the amount is indexed for inflation) in your lifetime (the lifetime federal exemption amount was doubled by the 2017 Tax Cuts and Jobs Act but starting 2026, the exclusion amount reverts to the 2017 exclusion level).