The below diagram represents a sample fault tree analysis

click to enlarge
Here Sub-system A is the entire system which is being evaluated.
The green cells indicate a scenario where the presence of either cause will result in a fault. Either 1 or 2 will result in a fault. (OR Logic)
The orange cells indicate a scenario where the presence of all causes will result in a fault. (AND Logic)
All 3 causes 3, 4 and 5 need to present to result in a fault.