An electrode is a conductor that is used to make contact with a nonmetallic part of a circuit. Electrodes are commonly used in electrochemical cells, semiconductors like diodes, and in medical devices. The electrode is the place where electron transfer occur.
An electrode is classified as either a cathode or an anode depending on the type of chemical reaction that occurs. If an oxidation reaction occurs at an electrode (oxidation being the loss of electrons), then the electrode is classified as an anode. If a reduction reaction occurs at an electrode (reduction being the gain of electrons), then the electrode is classified as a cathode.
More information on electrode here
You might also want to read Diode