The OR block receives data with two inputs, then sends the data from the input that received data first. The OR block is useful in flows where there are two paths leading to the same block (like an Output block) and only one path has data in a given run. Routing two paths through an OR block prevents the final block from waiting for data from both paths.
The OR block has two input ports. You can only connect a single block to each input port. The first input port that receives data routes the data to the output port.
The OR block has a single output port. It sends data from the input port that received data first.
To see the OR block in an example flow, check out Flow Snippets: OR.