As per the EU standard guidelines:
FFP1 masks are the least filtering with a 20% of aerosol leakage to the inside. Before the pandemic these masks were mainly used as dust masks.
FFP2 masks allow a maximum of 8% of aerosol leakage to the inside and are commonly used in construction, but also by healthcare professionals.
FFP3 masks are the most effective, letting only 1% of aerosol leaking in and are mainly used in the chemical industry.