Watch tutorials…
This is a great series that goes over pretty much EVERY node: https://www.youtube.com/channel/UCOVfF7PfLbRdVEm0hONTrNQ
Watch the Unreal Engine channel as they have tons of tutorials.
Its very tough for folks here to completely explain what this or that node is, but all of that information is out there in tutorials / documentation.
teak