The “TULIP” acronym may be of recent vintage, but it works and gives us a bumper-sticker version of the Canons of Dordt.
T = Total Depravity
Maybe “Thorough” is a better term. All human beings throughout history, except Adam and Eve originally, and Jesus, were, are and will be sinful. Furthermore, this sin means that, whatever noble and good things one finds in a human being, one will never find anyone, of themselves, producing true faith in God and repentance from false gods or “gods.” This sets us up for the next second and especially the fourth letter in the acronym.
U = Unconditional Election
Out of their depraved and guilty state, God chooses to have mercy to everlasting life on some but not on all. He chooses these people on the basis only of his mercy, not on the basis of any relative merits they might have compared to others, or any other supposed or real good works they allegedly have done or will do in the future. He chooses to bring to bring these people to everlasting life and, unless he so chooses, they will resist his offers of mercy just like everyone else (see T above).
L = Limited Atonement
Some people claim that, by sending his son to die and rise, God was only attempting to save all humanity or as much as humanity as he hoped was possible. It is true that the cross represents God’s love to all who hear about it and that any hearer should respond to the message by faith and repentance. But God did not forget his intention for history and for individuals in sending his Son to bring obtain salvation for all who would obey him. He had those particularly in mind throughout history that he had unconditionally chosen (see U above) from eternity. He sent his Son especially for them and, in that sense, for them only.
I = Irresistible Grace
Just as all people are inherently oriented to be hostile to the true God (see T above) so God is able to change them so that they willingly repent and believe the Gospel. There is no one so evil or unbelieving that God cannot change them in this way by his unmerited blessing of the Holy Spirit given through Jesus Christ.
P = Perseverance of the Elect
Those whom God has chosen for eternal life (U above) and has morally transformed by Jesus and the Spirit (I above) will, despite any wavering during life, ultimately persevere in faith and so inherit eternal life. No one else will do so.