Why An electrolytic capacitor uses a very thin oxide layer formed on the aluminum (or tantalum) foil as its dielectric, and since capacitance goes up as the dielectric gets thinner, that construction packs a very large capacitance into a small package. That is why values of tens or thousands of microfarads come in parts the size of a thumb, while a film capacitor of the same value would be huge. The tradeoffs are wide tolerance, noticeable leakage current, high internal inductance and a polarity that must be observed.
Watch out Tight tolerance and very low leakage describe good film, mica or ceramic capacitors; electrolytics are among the worst on both counts. They are also poor at RF because of their series inductance and resistance, so they are used for power supply filtering and audio bypassing, not RF tuning.
Electrolytic = big farads in a small can, but sloppy, leaky, polarized and not for RF.