"Like Dissolves Like"
Is what chemist use to remember how "polar" and "non polar" solvents and solutes work.
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.
An example would be, water is polar and oil is non polar. When water is mixed with oil water will not dissolve in oil.