What are "strings" when you are talking about the string theory?

Shoestrings.

strings are the smallest possible objects.   they represent the source of forces in our universe.  

Actually there might not be any objects at all.    
forces:
Mass and gravity
Magetism and electric fields
weak nuclear force
strong nuclear force.

those four forces are actually what we percieve as reality.   There doesn't HAVE to be an object to represent the location where a force eminates from.

good luck!

String theory is a mis-nomer.  What physicist are really talking about are vibrations or oscillations.  Instead of thinking of the fundamental particles of nature as infinitely small hard spheres, think of them as places where the quantum field is oscillating.  There are many frequencies at which such a place might vibrate and each frequency determines the characteristics of that particular place.  The interactions of the frequencies gives rise to things like protons, neutrons, atoms and matter.  The world is just a bunch of frequencies.  Thats the essence of string theory.

1st sentence of Source 1:
String theory is a model of fundamental physics whose building blocks are one-dimensional extended objects (strings) rather than the zero-dimensional points (particles) that are the basis of the Standard Model of particle physics.

So the "strings" are one-dimensional extended objects.


Interresting factoid about the strings:
String theory is thought to include some 10, 11 or 26 dimensions, depending on the specific theory and on the point of view.

The fundamental particles of the universe electrons, neutrinos, quarks, etc., are considered to be pointlike (infinitely small points).  According to string theory, if we could examine these particles with even greater precision?a precision many orders of magnitude beyond our present technological capacity?we would find that each is not pointlike but instead consists of a tiny, one-dimensional loop. Like an infinitely thin rubber band, each particle contains a vibrating, oscillating, dancing filament that physicists have named a string.

The strings are still in theory. No one has actually seen it and no experiment has proved it. But physicists are doing lot of progress in this field to prove this.

What is string theory?
Physics explains the nature of the greater space with Gravitational theory and general relativity. It explains the nature of atoms, electrons, neutrons, protons etc., using electromagnetic theory and quantum theory. Now we couldn't use the gravitational rules to explain the nature of atomic and and subatomic particles. Likewise we couldn't explain the greater space using just electromagnetic and quantum theory. But logically we should have one rule which applies to everything in the universe. If not, the universe cannot survive as a whole. So there is a missing link between these forces(gravity, electromagnetic force, nuclear force). String theory tries to explain this.

So string theory is also called "Theory of everything"

You can find lot of information about this in the below link. They have a 3 hour video too on this which is simple to understand.
http://www.pbs.org/wgbh/nova/elegant/

They are smallest  possible objects .They are curly /like a rubberband. They have relation with mass,gravity, magnetism etc.

They're essentially miniscule -- much, much smaller than a quark -- rings of energy, compactified into 6 dimensions. Different vibrations of the strings create different particles.

they are the little underwear panties with a string ,you know where ? that i wear !yeahhhhhhhhhhhhh

according to the string theory(just the outline)quarks move indepently in a nucleon but when one of the quarks are subjected to extrernal force the other quarks suddenly exert an infinite tension force on this quark so you cant take a quark out separately