A more thorough explanation:

A master trust is a type of investment vehicle that combines assets from multiple sources for collective management. It is similar to a pooled trust, where assets are managed in a central fund.

For example, an employer can use a master trust to pool the investments in a pension or employee benefit plan. This allows the portfolio manager to manage a single pool of investments, which can reduce transaction costs and provide access to less expensive share classes and overall fees.

The benefit of a master trust is that it provides greater economies of scale, which means that investors can pool their investments together. This can result in lower costs and better returns for everyone involved.

Overall, a master trust is a useful tool for managing investments and can be particularly beneficial for large organizations with many investors.