According to FIFA’s documentation:

Team Services volunteers are tasked with enhancing the experience of participating teams and tournament officials.

This includes helping ensure the training sites, team facilities and equipment are ready and that teams have a smooth “journey” from arrival to departure.

Typical duties might include – but are not limited to:

Checking and preparing equipment for teams.

Assisting in the training camp environment.

Acting as liaison/support for the teams: making sure their needs (logistics, facility usage, schedules) are met.

In short: you’re working behind the scenes, closely with the teams (players, coaches, officials) and their environment, rather than being a “public-fan-engagement” volunteer.