The hadith of Jibril
Sahih Muslim (8) reports from Umar ibn al-Khattab (may Allah be pleased with him) that the angel Jibril (Gabriel) came to the Prophet ﷺ in the form of a man and asked him about Islam, iman (faith) and ihsan (excellence). When he asked about iman, the Prophet ﷺ answered: "To believe in Allah, His angels, His books, His messengers and the Last Day, and to believe in the divine decree, its good and its bad." Sahih al-Bukhari (50) has a similar report from Abu Hurairah.
The same report says that Islam means the five pillars, and that ihsan means to worship Allah as if you see Him, knowing that He sees you.
This report shows that faith and practice go together. The beliefs below are the base, and good actions grow from them.