The main difference is what they cover.
A health & welfare LPA covers decisions about things like your medical treatment and care, your daily routine, where you live, what you eat and drink and who can visit you.
In contrast, a property and financial affairs LPA covers decisions and actions around things like your home and assets.
Another difference is when they can be used. A health and welfare LPA can only be used when you no longer have the mental capacity to make such decisions for yourself. In contrast, a property and financial affairs LPA can be used at any point you need help making decisions relating such matters.