Hyperconjugation is the stabilising interaction that results from the interaction of the electrons in a s-bond (usually C-H or C-C) with an adjacent empty (or partially filled) p-orbital or a p-orbital to give an extended molecular orbital that increases the stability of the system.

Based on the valence bond model of bonding, hyperconjugation can be described as "double bond - no bond resonance" but it is not what we would "normally" call resonance, though the similarity is shown below.

What is the key difference between hyperconjugation and resonance ?

"hyperconjugation involves a sigma orbital component, resonance is just pi orbitals " 

Hyperconjugation is a factor in explaining why increasing the number of alkyl substituents on a carbocation or radical centre leads to an increase in stability.
 

The stabilisation arises because the orbital interaction leads to the electrons being in a lower energy orbital
 

Of course, the C-C s-bond is free to rotate, and as it does so, each of the C-H s-bonds in turn undergoes the stabilising interaction.
So the ethyl cation has 3 C-H s-bonds that can be involved in hyperconjugation.
The more hyperconjuagtion there is, the greater the stabilisation of the system.
So for example, the t-butyl cation has 9 C-H s-bonds that can be involved in hyperconjugation. Hence (CH₃)₃C+ is more stable than CH₃CH₂+
The effect is not limited to C-H s-bonds, appropriate C-C s-bonds can also be involved in hyperconjugation.

hope u would have got evrythin clear...........