There are around 3500 different types of fungi here in the UK alone and I have always found the shapes, sizes and colours fascinating, and the very nature of where a good deal of them choose to grow can mean that photographing them can be challenging to say the least! Over the years I have built up a good knowledge and understanding about this amazing world and have learned to identify with a good degree of confidence the most commonly encountered species.
Please note however that if you are thinking of taking up an interest in this subject you MUST make sure you seek the guidance of an expert before venturing out to pick anything. There are some species that can be very dangerous if ingested. http://www.dorsetfungusgroup.com/ is a good place to start!