Programmability
A hearing aid is not a personal amplifier and the main difference between them is programmability. Generally hearing amplifiers amplify all frequencies while hearing aids while hearing aids are specifically made to optimize sounds you have trouble hearing.
Ask your audiologist about pre-programmed settings and how it feel like to use in different circumstances like at home versus at the park. A hearing aid should be sensitive to sounds of certain frequencies otherwise all sound is amplified uniformly and that will only make things worse.