Answer: An accounting programme that you can use to monitor the value of your cryptocurrencies.
You can use your portfolio to fictionally track the value of your cryptocurrencies. You can enter your cryptocurrencies and the amounts you possess yourself. Because this is a fictional programme, you can also enter the cryptocurrencies you manage through external wallets. This allows you to see their value and any profit you have made at a glance.
Note; the portfolio is no more than a programme you can use to track the value of your cryptocurrencies. That means that you can decide the cryptocurrencies you enter and their amounts. If this is incorrect, the value of your portfolio will not correspond to the actual value of your cryptocurrencies.