Like Dissolves Like
"Like dissolves like" is an expression used by chemists to remember how some solvents work. It refers to "polar" and "non-polar" solvents and solutes. Water is polar. Oil is non polar. Water will not dissolve oil. Salt is ionic(which is extremely polar), and water is polar. Like dissolves like, that means polar dissolves polar, so water dissolves salt.
Polar substances will dissolve in Polar substances
Non-polar substances will dissolve in non-polar substances
Non-polar substances will not dissolve in polar substances.