The coinmarketcap marketcap app has some features that you will also find on the website, things like prices, exchange data, watch list live price updates, and so many other interesting features. You can also create a portfolio and track it when you create an account with them. Being able to track one's portfolio is an interesting feature because it allows people to track their portfolio in real-time. The prices are coming from the CMC data, you do not have to worry about it the data is real because you can be assured that you are getting some of the most accurate market rates.
This is a button at bottom of the page on the app that can take you to where you can access all this information in the portfolio tab. You will be able to see your top holdings in percentage terms as well as the dollar amounts, you can also view it pie chart. You will be able to see your best-performing asset and worst-performing asset in your cryptocurrency portfolio. Not only can you track one portfolio, but you also can add multiple portfolio. If possible you do not have your phone on you, you can view your portfolio on Coinmarketcap website.