Monounsaturated fat is liquid at room temperature and may solidify in the fridge. It is a non-essential fat that is credited as a major contributor to the health benefits of the 'Mediterranean diet' (lower heart disease for example). 

Mono-unsaturated Fats (MUF)

The first suggestion that MUF are associated with beneficial effects upon the heart comes from the ‘Seven Countries Study’ in the 1960s. In this multicentre study it was observed that, after World War II, people from Greece, and other parts of the Mediterranean basin, had a low frequency of heart disease, despite the high fat intake of the diet.

The major source of fat in their diet came from olive oil, which is rich in MUF, as opposed to saturated animal fat, commonly consumed in nations with higher rates of heart disease. This is now commonly referred to as a ‘Mediterranean diet’ (MD).

Foods typical of the MD include fresh vegetables and fruit, nuts, legumes, whole grains, herbs and seed, eggs, red wine with meals, and infrequent consumption of meats1.
.
A large clinical trial from Spain found that a MD, containing nuts and extra-virgin olive oil and optimal sources of MUF, reduced heart attacks and strokes, when compared with a lower fat diet containing a higher proportion of carbohydrate2.

291

445

https://www.checkyourfood.com/content/blob/Micronutrients/top-foods-for-Monounsaturated-fats.jpg