Genesis 3:14-15 meaning

God cursed the serpent. A curse is the direct opposite of a blessing and shouldn't be confused with profanity in a modern sense. The word "cursed" used here is the Hebrew word arar which means to "set apart in order to afflict misery or judgment." God curses the serpent, ranking it last in the order of all other animals and forcing it to crawl in the dirt. The phrase expresses the humiliation that the serpent received from God. We see this phrasing in the Old Testament book of Micah 7:17, "They will lick the dust like a serpent, like reptiles of the earth. They will come trembling out of their fortresses." This curse appears to have had impact on the creature the serpent, which previously did not crawl in the dirt, and upon Satan, who will have his head crushed (as anyone who encounters a viper is inclined to do).

Genesis 3:15 is an important verse in the Bible. In it we see the first promise of the Messiah (savior). God puts enmity (hostility or hatred) between the woman and the serpent and between their descendants (v 15). The seed of the serpent signifies evil spirits and wicked people, serving Satan, while the seed of the woman is a reference to all of humanity but ultimately of Christ and all those in him. Satan would bruise the heel of humanity, tormenting them with sin and death, as well as causing Christ to be crucified. But ultimately, Christ will crush his head ending sin and death. This defeat of Satan is mentioned in the last book of the Bible: 

"And the devil who deceived them was thrown into the lake of fire and brimstone, where the beast and the false prophet are also; and they will be tormented day and night forever and ever"
(Revelation 20:10).

Jesus defeated death when He resurrected (1 Corinthians 15:54-55), but its final demise will not occur until the end. This is also recounted in the last book of the Bible: 

"Then death and Hades were thrown into the lake of fire. This is the second death, the lake of fire"
(Revelation 20:14).