Beta measures how much a share has tended to move when the market moves. A beta of 1 moves in line with it, 1.5 tends to move half as much again, and 0.5 about half as much. What it captures is systematic risk, also called market risk: the part of a share's movement that comes from the market as a whole, which no amount of diversification removes.
It doesn't measure almost everything else. A low-beta share can still collapse for reasons of its own — fraud, a failed product, too much debt — because company-specific risk sits outside beta. It's also worked out from past prices, so it describes a past relationship rather than promising a future one. In the app, it's the Beta figure in a holding's detail, and it feeds the market-sensitivity measure in the health score. It reads N/A where the data provider has none, which is the case for most funds. A low number there means the share has moved less with the market, not that it's safe.
Tended to: beta describes a past relationship, and only the market-wide part of the risk.
Educational content only. It is not personal financial advice.