Fund managers can sometimes have a 'theme' that they are employing within a portfolio.
For example if a theme such as “health and wellness” is targeted fund managers will only want to consider funds that invest in healthy food brands or those companies focused on developing new vaccines.
A further theme example could be “green investing”.
In this scenario fund managers will only invest in companies and technologies that are considered good for the environment for example alternative energy generators or energy-saving technology manufacturers.