I found stackoverflow very helpful while I was first picking up Git terminology. Questions like these ones were really useful for me (mostly because of their conciseness) and I kept them open in tabs during the first couple of weeks I used it. Maybe print out a couple of the answers in bold? Especially the diagram on the first one.

https://stackoverflow.com/questions/2745076/what-are-the-differences-between-git-commit-and-git-push

https://stackoverflow.com/questions/292357/what-is-the-difference-between-git-pull-and-git-fetch

I also found a visual representation of the trunk to be amazingly useful but you're already covering that one with SourceTree.

_{Aside, this bit probably belongs in a comment but I lack the rep: I'm one of the junior consultants mentioned in the question. Before I started I had some idea what a source control system was and I'd poked SVN literally twice, Gusdor gives me more credit than I deserve. The whole team had high-quality specialised Git training, toys and time to play. The problem is not with Gusdor's instruction. I hope there's a good alternative solution to this so I can bookmark it hard and learn more.}

I found stackoverflow very helpful while I was first picking up Git terminology. Questions like these ones were really useful for me (mostly because of their conciseness) and I kept them open in tabs during the first couple of weeks I used it. Maybe print out a couple of the answers in bold? Especially the diagram on the first one.

What are the differences between “git commit” and “git push”?

What is the difference between 'git pull' and 'git fetch'?

I also found a visual representation of the trunk to be amazingly useful but you're already covering that one with SourceTree.

_{Aside, this bit probably belongs in a comment but I lack the rep: I'm one of the junior consultants mentioned in the question. Before I started I had some idea what a source control system was and I'd poked SVN literally twice, Gusdor gives me more credit than I deserve. The whole team had high-quality specialised Git training, toys and time to play. The problem is not with Gusdor's instruction. I hope there's a good alternative solution to this so I can bookmark it hard and learn more.}