Thanks to Ron Barrow for this helpful example of how to use probability tree diagrams. 158,411 views is impressive! You need to know this if you are taking the GCSE Higher paper.
This video by Luke Redding is also very clear and takes the topic a bit further because it includes experiments where the item is not replaced.
Maths is fun also explains this well and includes some interactive questions. GCSE Bitesize is another good site to test yourself on this.