Temporal clauses are subordinate clauses that give information about time: when something started, how long it will last, etc.
They always begin with a temporal conjunction - there are quite a few, and each has a different meaning.
Meaning: "seit" expresses when something started (only use when it's still going on)
Meaning: "bis" expresses when something will end
Meaning: "während" expresses that things are going on at the same time
Meaning: "solange" expresses that an action will continue as long as another action continues to occur
Meaning: "nachdem" expresses that one thing happened after another (the events of the subordinate clause happen first, then the main clause)
Meaning: "bevor" / "ehe" expresses that one thing happens before another (the events of the main clause happen first, then those of the subordinate clause)
"Bevor" is used much more often than "ehe."
"Bevor" and "ehe" are opposites of "nachdem."
Meaning: "sobald" and "sowie" express that something (the main clause) happens right after something else (the subordinate clause)
In order to make sense, we put the subordinate clause one temporal stage (one tense) before that of the main clause.
Difference between "sobald" / "sowie" and "nachdem":
When you use "sobald" / "sowie," the second action happens directly after the first action is completed. With "nachdem," it just happens at some point after the first action is completed.
The temporal conjunctions and their meanings:
An overview of subordinate clauses.