Both are ways for an organism to adapt to the environment, but enantiostasis focuses on maintaining functionality while homeostasis focuses on maintaining a stable internal environment.
For example, if the organism has to deal with changing salt concentration in water, it can do it in two ways:
- Homeostasis : the organism will adapt itself so that its internal conditions do not change despite the change in the external environment (the focus is on not changing these conditions). This could mean stopping or reducing other activities because of this adaptation, but, in this example, the internal conditions (salt concentration inside the organism) will not change.
- Enantiostasis : the organism adapt itself so that its functionality is preserved, at the possible expanse of stable internal conditions. This could mean the salt concentration in the organism will change, but the organism's functions will not stop or be reduced because of it. Enantiostasis can be realized either by avoiding external changes (for example, absorbing more water when the salt concentration is high and less when it's low) or tolerating it with a wide range of possible conditions.
(Source : detailed explanation on this subject as a commentary on a university course)