The assets legally belong to the minor but are controlled by the adult until the minor reaches the "age of majority" (usually 18 or 21, depending on state law).
In the United States, you typically cannot buy stocks independently if you are under 18 because minors lack the legal capacity to enter into binding brokerage contracts. However, you can still own and invest in stocks through specialized account types managed with adult supervision. Legal Ways to Buy Stocks Under 18 : can you buy stocks under 18
Some brokers, such as Fidelity and Charles Schwab, offer accounts for teens aged 13–17. The assets legally belong to the minor but
(Uniform Gifts to Minors Act) is for financial assets like stocks, bonds, and mutual funds. Legal Ways to Buy Stocks Under 18 :
Available if the minor has "earned income" from a job (like a part-time job or even neighborly chores).