Fondo is a word that has many meanings in English. It depends on how it is used as to how it is translated.

Fondos can mean funds, as in financial funds.

It can mean background, such as background music or a set for a video or stage production.

Fondos can be the core or essence of something.

Endurance sports can use the word fondo too. A corredor de fondo is a long distance runner and cross-country skiing is esquí de fondo.

Those are just some of the many usages for the word fondos.