what's the difference between an infantry officer and guardsmen

Officers in any trade or capbadge are the ‘managers’. Soldiers work through the ranks on promotion to become junior and middle management. Soldiers can also commission and become officers.

Will,

An officer will go to the military academy Sandhurst to commission and a guardsmen will go to the infantry training centre in catterick.

As mentioned above, officers take a management role and spend the majority of their day behind a computer. They deal with some tactics on the ground when on operations.

A guardsman will be the boots on the ground doing the cool stuff. The higher you promote through the ranks the more time you’ll spend at a desk in a managerial role as expected.

Search on the army website at both job roles, they are both at total opposite ends of the spectrum