An information flow diagram is an effective way to understand a solution architecture - it is easy to create and intuitive for your audience. This "101" will get you creating them in no time!
Business analysis is the art and science of identifying business needs and determining solutions to business problems. Solutions sometimes include a technology component, but may also consist of process improvements, organizational change, or strategic planning.
We view the technology solutions aspect of this to be solution architecture and focus our business analysis topics on eliciting and documenting current and future state processes and requirements.