What does matrix mean?

Hint: As we know that a matrix is a collection off numbers, which are organised in rows and columns. Or we can say that it is an array of numbers arranged in a rectangular way and they are divided between rows and rows. It is written by writing all numbers within the square braces. There are several types of matrices.

Complete answer:
We can say that a matrix or in plural we can say matrices, is a rectangular array or table of numbers, symbols or expressions that are arranged in rows and columns. We can represent it as $ m \times n $ where $ m $ rows are horizontal and $ n $ columns are vertical. An example of a matrix is
 $ \left( {\begin{array}{*{20}{c}}
  {{a_{11}}}& \ldots &{{a_{1n}}} \\
   \vdots & \ddots & \vdots \\
  {{a_{m1}}}& \cdots &{{a_{mn}}}
\end{array}} \right) $ .
It is symbolised as $ {A_{m \times n}} $ . There are several types of matrix, A column matrix is a matrix which has numbers as elements only in a single column. We can define a row matrix which has numbers only in a single row while a square matrix is a matrix with an equal number of rows and columns.
We can define a diagonal matrix as a special type of matrix which has elements only in the leading diagonal and all the other elements in the matrix are $ 0 $ .

Note: We should note all the important properties of matrices as they are very useful while solving questions. Matrix multiplication can only happen when the number of columns of the first matrix is equal to the rows of the second matrix i.e. no of rows of first matrix $ \times $ no of columns of second matrix. In the product of matrices $ A \times B $ , $ A $ is called the pre factor and $ B $ is called the post factor.