1. Solubility:
Dissolution: is the process of a particle (solid) become incorporated into a liquid so as to form a solution.
When you put a teaspoon of salt in water, the salt dissolves in the water and the solid crystals disappear. We call the salt solute, the water solvent and the end product solution.
Water molecules are high polar, therefore when sodium chloride dissolves, the positive (hydrogen) side of water are attracted to negatively charged chlorine ions, and oxygen side attracted to sodium, causing them to separate and integrate into the water.

2. Would everything dissolve?
The answer is no
There are a few things that determine if a substance will dissolve or not:
The within solute forces
The within solvent forces
The forces between solute and solvent
And for a solute to dissolve, the solute-solvent forces must be equal or stronger than the solute-solute and the solvent-solvent forces.