The majority of conjunctions are "subordinating conjunctions". Common subordinating conjunctions are:
A subordinating conjunction joins a subordinate (dependent) clause to a main (independent) clause:
Look at this example:
A subordinate or dependent clause "depends" on a main or independent clause. It cannot exist alone. Imagine that somebody says to you: "Hello! Although it was raining." What do you understand? Nothing! But a main or independent clause can exist alone. You will understand very well if somebody says to you: "Hello! Ram went swimming."
A subordinating conjunction always comes at the beginning of a subordinate clause. It "introduces" a subordinate clause. However, a subordinate clause can sometimes come after and sometimes before a main clause. Thus, two structures are possible: