In a block diagram, signal flow is represented by the wires that connect one block to another. The triangular connectors on blocks indicate the direction of signal flow. Their color indicates the type of data being transmitted. Scalar signals are represented as thin wires; vector and matrix signals are represented as thick wires.
You can also transmit signals using variables. A variable lets you name and transmit a signal throughout a block diagram without using wires. Typically, you use a variable block for system-wide variables or signals that would be laborious or visually messy to represent as wires.
You can manually bundle and unbundle signals using the scalarToVec and vecToScalar blocks.