Alpha
The annual return left over after subtracting what your market exposure explains.
How it is computed here
Jensen's alpha: your return minus the risk-free rate plus beta times the index's excess return.
Worked example
This one compares the portfolio with an index you choose, and the demo portfolio has none set — so there is no honest example to show here. On your own portfolio, choose a benchmark on the dashboard and it appears.
Where it misleads
It is meaningless when R² is low — that says the index does not describe you, and the leftover is measuring the wrong comparison rather than skill.