Adding phrases to a complete sentence

Hi,

1)
Firsty, I know independent clause, dependent clause and that a phrase is when it is a group of words without a subject-verb relationship; however, are there more types than these three?

With this in mind, if one has wrtitten a complete setence, is it correect/allowed to have phrases added to it every time?

That is, is it correct to have a phrase added to an independent clause every time as long as a comma separates the two? And does the comma have to be present?

2)
And secondly, when one breaks up a sentence and identifies (if it is a complex sentence) the two clauses and (a) phrase(s), do commas usually need to be used to separate dependent clauses and independent clauses from phrases?

For example, I was walking home bringing the food back to my friends.

I was walking home=indep clause
bringing the food back to my friends=phrase, as no subject

Here is an example where I know I need a comma to separate the two parts of the sentence, but why is it it different from the above sentence?

It was a really nice day, wanted to go surfing.

So, when does one know when a comma is needed to separate the phrase from the independent/dependent clause?

3)
Also, is there a difference between a conjunction and a coordinating conjunction?

4)
Finally, is whereas a conjunctive adverb or is it just a conjunction? I need to know how it should be punctuated when joining clauses.

Thanks a lot!!