What is the use of matrices?

I'm new to this concept and I wanted to know how useful is to use a matrix. Give me an example of a simple problem and a difficult problem that could be solved with this tool.

matrices are used to mathematically express systems of linear equations, used in many fields of physics and most important, for calculations done with computers, since matrices are fast and effective to operate. What are you going to study?

I don't know exactly what am I going to study, but something around physics and/or mathematics.

I already found many mathematic-related books about this and that. Yesterday I found one about matrices which interested me because it said matrices were very used in computers.

I'm still in highschool so I need to know if it's a good idea to invest my time in this or not. What you said is still a bit vage to me, can you give a more concret example?

matrices start to show up at uni now, in electronics and control Engineering, i expect they show up everywhere where you do more advanced calculations on physical systems.
You won't have need for them soon, but if you really want something interesting, try making your own 3d-engine, and you'll see how usefull matrices are for rotation movement and projections ;)

u can solve linear equations using matrix..
try this java applet
http://www.ma.psu.edu/~herzog/applets/lin_equation/