Buying Stocks: Typically, when you buy stocks at a traditional brokerage firm, your investments are tracked independently, and you don't have a view on your overall portfolio balance and performance. This leads individuals to pick one stock at a time, without an understanding or view on their investments as a whole. At dub, we believe that looking at your investments through a portfolio lens provides a more holistic understanding of your overall risk and diversification of all your assets. It's for this reason that we don't provide individual stock trading in a traditional sense. Instead, we encourage the development of a portfolio.

Investing in Portfolios: When you copy a portfolio, you are purchasing the portfolio's underlying assets (e.g. stocks and ETFs) in the same proportions held in the portfolio you have copied. Your investment performance therefore is an aggregation of the performance of each underlying asset in the proportions in which you hold them in the portfolio. 

Portfolios are a great and easy way to achieve investment diversification! See What is a Portfolio?