Both answers are too simplistic- Mr Veilleux's response, at least touches the surface & does state "the simplest questions are the hardest to answer"
This is because this is NOT a simple question.
There are MANY causes of back pain, most not serious but ANY that are chronic, are very problematic & to diagnose the cause for same is important & can be difficult.
Without a cause, the proper treatment is less likely (except by accident).
Acute is "simple"- stay as active as possible & don't do anything that makes the pain worse; there are many palliative treatment, that can help feeling better, healing, lessening injury or muscle spasm- the proper choices depend on the reason for the back pain- heat or cold/ice, massage etc. are not appropriate for all causes.
If long lasting (more than a week) OR getting worse, OR added symptoms- then proper medical diagnosis is imperative.
Once chronic (which can be due to early mis-diagnosis or improper care), than a medical diagnosis must be made.
I won't list the MANY causes, as that may cause needless worry, but the correct diagnosis must be made ASAP. (For acute or chronic- acute must be resolved properly or it may become chronic).
Chester Suske DO, FACOFP

I don't believe there are only "3-types" or causes for back pain, in my answer I said there are "MANY", & all of the causes or types would be too numerous to be listed here,
(there are BOOKS written about this).
To be simplistic, you might say:
pain from -
1. bones/joints
2. Muscles/fascia
3. nerves
but, there are many causes of pain & subgroups of these 3, & sometimes all 3 at once.
Doc

Of course my "3s" are the major causes of back pain
- the ones mentioned by Mr Lane are descriptors- the When , Where & What's of pain-
where is the pain, (& whether it's diffuse or local);
when did it start (how long has it been present) = acute or chronic,
what type of pain is it - multiple descriptors apply here, for types of pain sensations
(& associated symptoms/other sensations- ie. numbness, etc.)
doc