The main aspect used to differ coniferous tree are their leaves. Coniferous leaves look like elongated needles, instead of the regular flatend out leaves we're used to
Further characteristics:
Seeds are hard and grow in large groups, stuck to eachother.
Coniferous are evergreen trees (don't shed leaves nor change the colour of these, although this rule does not apply to all of them).
They have spread worldwide.
Can withstand low temperaurees and can be found even in places like the Artic circle.
I've pasted some images down below that might help you a lot. (Left - leaves; Right - coniferous trees).
Hope it helped,
Happy homework/ study/ exam!