What does equity mean?

In regards to home ownership and property, equity can be seen as:

Home appraisal value (minus) loan amount (equals) Equity amount

It is possible to have negative equity, which can happen when a homeowner buys in a rising market, and there is a price correction, reducing the value of the home appraisal. If there is no loan against the home, the equity is equal to the appraised value.

Equity can also be viewed as Share.