Ganesha Chaturthi is very dear to Shree Ganesha. Chaturthi means fourth stage. Ganapathi is beyond three stages of human body i.e. awakened stage, dreaming stage and a middle stage between these two stages. When Ganesha is in his fourth stage, one can have his Darshana. Hence Chaturthi has special importance and devotees observe this by fasting and offering Poojas to the Lord.
Sankashta Chaturthi (Sankashti) : This vow is done by devotees on fourth day of second fortnight of every month. On this day devotees fast for whole day & break their fast after having darshan of Lord moon and worshipping Lord Ganesha. This vow is observed strictly by devotees to get rid of problems in their life. On this day in the evening, after having bath , worship Lord Ganesha by decorating him with kumkum, flowers and Durvas, offer Naivedya and perform Aarti while chanting mantras and shlokas. Then have a darshana of Lord moon, offer him Naivedya and break your fast by eating the Prasada. Follow this vow and get the blessings of Lord Ganesha.
Vinayaka Chaturthi : Fourth day in the first fortnight of every month is called as Vinayaka Chaturthi. This vow is to be observed for full day.
Angaraka Chaturthi : If Sankashta Chaturthi comes on Tuesday, it is called Angaraka. The vow is completed on the same day. Devotees have their meal in the night after having darshana of Lord moon.