Conjunctions combine words, phrases, and clauses with each other.
There are two main types:
Coordinating conjunctions combine equal elements with each other: main clauses with main clauses, subordinate clauses with subordinate clauses, words with words, phrases with phrases, and sentence elements with sentence elements.
The coordinating conjunctions are: "außer," "denn," "und," "oder," "aber," "doch," and "sondern."
Multipart conjunctions are a special type of coordinating conjunction. As their names suggests, they are made up of two parts.
Multipart conjunctions don't have any effect on word order.
Multipart conjunctions usually come right before the part of the sentence they are related to. More info here: Multipart Conjunctions.
Subordinating conjunctions combine main clauses and subordinate clauses.
Subordinating conjunctions always come at the start of the subordinate clause, and the clauses are separated with a comma.
The most important subordinating conjunctions:
You can find a list of ALL the subordinating conjunctions (all the words that send the main verb to the end of the clause) as part of my Package of 40+ Grammar Lists.
Info about German conjunctions in general.
In addition to conjunctions, there are also conjunctive adverbs.