New levels of experience give us access to:
- more skill points that we can spend on skills
- additional abilities (powerful "perks") that we can unlock every 3 levels
- access to new kitchen interior design options
We reach new levels by getting the right amount of experience points - they are counted only at the end of the day. This is one of the main pillars of progression in the career mode, and to make things nicer, the system also gives us new recipes.