You're buying tokens that track the value of real-world stocks and ETFs
Your investment will go up and down with those assets. You should treat this as an investment in equities, with all the associated risks, including the possibility of significant loss.
You're not becoming a registered shareholder of any company
You hold a token on a decentralised exchange that reflects the price of the underlying asset. The legal rights attached to that token are set by the token's issuer – make sure to read their terms before investing.