Linguistically Taqwa means forbearance, fear and abstinence, but in the Islamic terminology, Taqwa has a distinct meaning. Taqwa is a high state of heart, which keeps one conscious of Allah's presence and His Knowledge, and it motivates him to perform righteous deeds and avoid those, which are forbidden.
The essence of Taqwa is to make a shield (which guards) against Allah's anger and punishment. That shield is to obey His commandments and abstain from His punishment. [as explained by Ibn Rajab (rahimahullah) in Jami al-Uloom wal-Hikam (190/191)]
Allah says: "O you who believe! Have Taqwa of Allah, as you should have of Him and do not die except as Muslims." [Soorah aal-Imraan (3): 102]
Ibn Mas'oud (radhiallahu anhu) said speaking about this verse, Allah is meant to be obeyed, and not disobeyed; remembered at all times, and not forgotten; and to be thanked; and we are not to be ungrateful to Him." Talq Ibn Habeed (a tabi'e) said: "Taqwa (piety) is that you act in obedience to Allah, and hope in His Mercy, upon a light from Him; and Taqwa is leaving acts of disobedience to Allah out of fear of Him, upon a light from Him." [(Saheeh) by Shaikh al-Albanee. Related by Ibn Abee Shaybah in Kitaabul-Emaan (no: 99)]