use of that/which between the sentence

Sentence is - We provided her all the basic things that are necessary to start a business.
In this sentence instead of that can we used which also. will that be correct.
wil somebody clarify in which condition that and which are used.

The difference between which and that lies in whether the relative clause is restrictive (ie: necessary information so no commas) or non restrictive (only extra information, so you put commas).  If it is non-restrictive you cannot use that.

So in your above example, you need to use that, the information is necessary to understand what these basic things are.

If you need some examples, see:

http://www.utexas.edu/courses/langling/e360k/handouts/obj_comp_mod/modifiers/rel_clauses/restric_rcs.html

use of that/which between the sentence

Sentence is - We provided her all the basic things that are necessary to start a business.
In this sentence instead of that can we used which also. will that be correct.
wil somebody clarify in which condition that and which are used.

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My corrections to your statement:

Use of that/which within a sentence

A sentence is: "We provided her with all the basic things that are necessary to start a business." In this sentence, instead of 'that' can we also use 'which'? Would that be correct? Please could someone clarify in what circumstances 'that' and 'which' are used.

That's a question that's difficult to answer!
That's a question difficult to answer!

That's a question which is difficult to answer!

All the above would be correct, though the first is best to a native ear, followed closely by the second, then the third.

In your sentence, you could, better, leave them out!:

"We provided her with all the basic things necessary to start a business."

It is 'provide ... with', or 'supplied ... with' or else, for example: "We gave her all the basic things necessary to start a business."

As to in general when 'that' and/or 'which' might be used, you might look up:

http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/learnitv313.shtml

But, I'd be inclined to say it is really a quite delicate matter that requires quite some hands on experience of English writing and speaking for one to be able to intuit what would be used in any given circumstance.

Or:

But, I'd be inclined to say it is really a quite delicate matter, which requires quite some hands on experience of English writing and speaking for one to be able to intuit what would be used in any given circumstance.

I think 'that' is better, in my two sentences, above (and 'that' may be preceded by a comma, as in the use of 'which', though the use of a comma before 'which' is necessary), but one or other of 'that' and 'which' is needed here and cannot be left out, unless one were to say, for example:

"But, I'd be inclined to say it is really a quite delicate matter, requiring quite some hands on experience of English writing and speaking for one to be able to intuit what should be used in any given circumstance."

Sorry that will probably seem complicated to you, but it is complicated!