title: Query about Properties Vectors in C++
body: <p>I am kind of a beginner and just came across the concept of vectors in C++. I have a few questions about it<br/>
  <b>
  1. Is there a concept of 2-D vectors in C++? if yes, then how do i declare corresponding to a 2-D Matrix a[n][m]? Here, n and m are variables.<br/>
  2. How are vectors passed as arguments to functions? By default are they passed by reference or by value?<br/>
  3. Are there any performance benifits of vectors over arrays in C++?
  </b></p>