With is a preposition. You will normally see it used to begin a prepositional phrase. For example, a sentence may read like this: John chose to attend the program with the best reputation. "With the best reputation" is a prepositional phrase that modifies program. A prepositional phrase can modify either a noun, or a verb. Most of the time it should be placed next to the noun or verb it modifies; however, if a short phrase comes in between and there is no other logical place to put the phrase, then this the phrase is allowed to come between the prepositional phrase and the word it modifies. Hope this helps.

I just posted about prepositions in my blog in the Strategy section. Its the grammar lesson for the day. I think you will find it helpful.