A long time ago in a business course I was taught about diagrams that help plan activities, and determine estimates of time required to complete a project: activities in the project were drawn as little circles; lines connected them to show dependencies and a number was assigned to each activity which represented the expected time of completion. The benefits of the diagram were mainly to estimate total completion time for the whole project, show what activities could be completed in parallel and when, and the critical path could be established which highlighted in which activities unexpected delays would cause a delay in the whole project. There were also additional refinements which I can't remember, so I would like to know the term for this analysis or diagram, so I can look for more information. I have tried googling, but am not getting anywhere.
My question: is there a name for this kind of diagram/analysis? I'm guessing there is a different name for this in mathematics to that for business project management? And probably computer science as well? It reminds me of a graph data-structure used in shortest-path algorithms for problems like satnav route finding. But originally was probably some sort of discreet mathematical problem?