What sort of habitats do they like?
Fungi will grow anywhere there is food for them. However, their habitat must be undisturbed (say unploughed, for example) and free from pesticides. So it is unlikely you will find them on well maintained lawns or parkland or on pathways. Undisturbed grassland may show the well know fairy-rings. They are simply areas where the reproductive or fruiting part of the fungus comes to the surface to release its spores. The mycelium or main body of the fungus lies below the surface of the grass.
Woodlands contain a great diversity of fungi. They have much to feed on there; dead leaves, dead trees, dead animals. Some fungi feed on living things. Trees are infected with many fungal diseases, of course some fungi have a balanced symbiotic relationship with trees. Scots pine, oak, beech and birch are associated with a rich biodiversity of fungi.
Some fungi are edible, but many are not. Never guess that you can eat one. Always refer to an expert if you want to include them in your diet. A good reference is How to Identify Edible Mushrooms by Harding, Lyon and Tomblin, published by HarperCollins.