In the past, individual investors had to buy one or more shares of a stock or ETF to make an investment.  If the price of one share was $100, that was the smallest amount an individual investor could buy.  However, it's now possible for companies like Stash to buy one share, and split it into parts, or fractional shares.  So if you want to buy $5 of an ETF share that costs $100, Stash can buy a full share, and have you own just a $5 fraction of that share.  That way, you can make small investments as a way to get started, you can invest in a more flexible way, and you can put more of your money to work.