Well, at a very high level, banks can use saved money to lend to businesses or individuals at a given multiplier. If a bank has insufficient deposits, it can't lend any more money. This is called fractional-reserve banking.
https://en.wikipedia.org/wiki/Fractional-reserve_banking So when you make a deposit, you are effectively causing a fraction of that deposit to be available for lending. This is what you're getting paid for when you get interest.
On the other hand, when you invest in a stock, you're providing liquidity to whoever held it last. That doesn't directly provide money to a company. But it has an important function: people only buy stocks when they are confident they can later sell it. If there were no buyers for stocks in the secondary market, nobody would participate in IPOs.
As far as which is better for the economy, this is beyond my knowledge. However, any normal person with any financial savvy knows that market returns are much better than deposit returns, so most of the time when such people say "save" they mean "invest in the market."
On the other hand, when you invest in a stock, you're providing liquidity to whoever held it last. That doesn't directly provide money to a company. But it has an important function: people only buy stocks when they are confident they can later sell it. If there were no buyers for stocks in the secondary market, nobody would participate in IPOs.
As far as which is better for the economy, this is beyond my knowledge. However, any normal person with any financial savvy knows that market returns are much better than deposit returns, so most of the time when such people say "save" they mean "invest in the market."