MyETF App is a selection and optimisation tool for ETFs, using modern portfolio theory for assembling an ideal portfolio of assets for the minimum level of risk. It is a formalisation of diversification in investing, the idea that owning different kinds of financial assets is less risky than owning only one type. Its key insight is that an asset's risk and return should not be assessed by itself, but by how it contributes to a portfolio's overall risk and return. It uses the variance of asset prices as a proxy for risk.

ETFs have a number of features that can make these investment vehicles ideal for young investors with small amounts of capital to invest. For one, ETFs make it possible to build a diversified portfolio with relatively low investment amounts. In addition, ETFs trade throughout the day, providing ample liquidity, and many have relatively low-cost structures. There are at least five reasons why young investors might want to consider ETFs for potential investment opportunities:

- Variety of ETFs
- Liquidity of ETFs
- Low fees of ETFs
- Index tracking with ETFs
- Keeping up with trends via ETFs

Many investors believe that the financial markets are governed by mathematical equations that are applied to the features of an asset's price and trading volume, among other factors. They evaluate rates of return and volatility to figure out which assets will perform best. One such method is modern portfolio theory, or mean-variance analysis, the process of assembling a portfolio of assets such that the expected return is maximized for a given level of risk.

A mean-variance analysis involves calculating the different volatility of portfolios, which is expressed as variance, and comparing it to the return. Optimal portfolios are then found on the efficient frontier, with maximum Sharpe ratio and minimum volatility representing the best risk/return ratio and overall lowest risk, respectively.