Free energy

It is unclear what free energy means. Help me ❓. There are 2 cases of free energy often considered:

• Gibbs free energy: $G:=H-TS$
• Helmholtz free energy: $F:=U-TS$ Where we, for the system considered:
• $H$ as the enthalpy
• $U$ as the internal energy
• $T$ as the absolute temperature, often measured in kelvin.
• $S$ as the entropy of the system