Questions

Resistivity :

Resistivity is a measure of the resistance to the flow of electrons. 

Conductivity :

Conductivity is just the inverse of resistivity, σ = 1/ρ, where σ is conductivity and ρ is resistivity.

Example:

Think of a pipe and water, the bigger the pipe, the easier water can flow and thus the lower the resistance. 

Oligopoly is market structure where a small number of large firms are there. Oligopolistic industries are characterized by a few dominant firms and substantial entry barriers.

It refers to the possibility for an investor to experience  losses due to  factors that affect the overall performance of the financial markets. Market risk cannot be eliminated through diversification, though it can be hedged against. The sources of market risk include natural disasters, recessions, political turmoil, changes in interest rates and terrorist attacks.

Exchange Traded Funds (ETFs) are a relatively new phenomenon and are gaining popularity rapidly. This post outlines the key features of an ETF.

ETFs are like mutual funds because they hold an underlying asset like stocks, debt, commodities future contracts etc. If you are new to the concept of an ETF, think of it as a mutual fund, and build your understanding from thereon. An example of an ETF is the SBI Gold ETF, which holds physical gold as its underlying asset.