What is the difference between a cathode and an anode?

Differentiate between an anion and a cation.

Will the size of the copper rod be affected in any way during the electroplating of iron with copper? 

Rani and her mother Sarojni were sitting outside in the verandah, talking about Rani's studies and career options. They saw some well-dressed people on the street, selling some items. Sarojni was intrigued and invited them to her house. These people told her that they were from a far-off state in India. They had come to Sarojni's state as a tourist but were robbed of all their money and documents. They only had one gold ring left, with a market rate of rupees sixty thousand, but they were willing to sell it for rupees twenty thousand as they were in urgent need of money. They showed the ring to Sarojni, who on examining saw that the ring was genuinely made of gold. On weighing the gold ring, Sarojni found that it would be worth rupees fifty-eight- to Sixty two thousand in the market. Sarojni wanted to buy the ring. She left the ring with Rani and went inside the home for fetching money. Looking at the ring, Rani remembered a process she had learned about in chapter Chemical Effects of electric Current of her science textbook. She took the ring and started rubbing it against a stone in her pocket. 
After rubbing it for some time, she took out the ring and saw that it was actually made of cheap metal with only a coating of gold. What is the process that Rani remembered?