The Sole One, The Incomparable.
Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ is Al-Ahad (in Arabic: ٱلْأَحَد), He is incomparable, unequaled, and indivisible. Al-Ahad is the One who was, is, and will ever remain alone. No one can ever be equal to Him in the essence of all His beautiful attributes.
From the root hamza-ha-dal (أ ح د), which has the following classical Arabic connotations: to be one, to be the only one, one alone, sole, to unite, unify.
Differences between Al-Ahad and Al-Wahid
As we mentioned previously, Al-Wahid and Al-Ahad are two names that describe the tawhid (the oneness) of Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ. He is the one who can neither be divided nor duplicated, making Him the one and only. This is the starting point of what it means to be a Muslim, the core belief from which everything else stems. That is why in the shahadah, we testify, la ilaha illa allahem>, "there is no god but Allah." He is said to be the one who existed before anything else existed. In this sense, He was the first. For a further explanation of His oneness, please view the section of Al-Wahid.
In this section, we explore the view of scholars explaining the difference between Al-Ahad and Al-Wahid, although both refer to His oneness. Each name of Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ is unique and offers a new shade of meaning. They are not synonymous, although there may be some overlap. Al-Ahad describes absolute oneness and uniqueness; none compares to Him. In contrast, Al-Wahid refers to His being as the numerical one. Some commentators noted that Al-Wahid indicates affirmation, whereas Al-Ahad refers to negation. For example, fi alhiqihi, lam ara ahada, "Actually, I didn't see anyone," and yabqa rajulun wahidun, "one man remains." Others note that Ahad is seen as conveying a higher degree. He is intensely one, uniquely one.
The name Al-Wahid is mentioned many times throughout the Qur'an. The name Al-Ahad appears in one place, and that is in Surah Ikhlas.
Qul huwal laahu ahad
"Say, “He is Allah, [who is] One," — (Qur'an 112:1)
Wa lam yakul-lahoo kufuwan ahad (section 1)
"Nor is there to Him any equivalent." — (Qur'an 112:4)
Sa'īd b. al-Musayyib reported in mursal form that the Prophet said, "If anyone recites ten times 'Say, He is God, One', a palace will be built for him in paradise because of it; if anyone recites twenty times two palaces will be built for him in paradise because of it; and if anyone recites it thirty times three palaces will be built for him in paradise because of it." 'Umar b. al-Khattāb said, "I swear by God, messenger of God, that we shall then produce many palaces for ourselves;" to which he replied, "God's abundant grace is even more comprehensive than that." 
The Love For Surah Ikhlas:
Anas said: One of the Ansar used to lead the Ansar in Salat in the Quba' mosque and it was his habit to recite Qul Huwal-lahu Ahad whenever he wanted to recite something in Salat.
When he finished that Surah, he would recite another one with it. He followed the same procedure in each Rak'a. His companions discussed this with him and said, "You recite this Surah and do not consider it sufficient and then you recite another. So would you recite it alone or leave it and recite some other."
He said, "I will never leave it and if you want me to be your Imam on this condition then it is all right; otherwise I will leave you."
They knew that he was the best amongst them and they did not like someone else to lead them in Salat. When the Prophet ﷺ went to them as usual, they informed him about it.
The Prophet ﷺ addressed him and said, "O so-and-so, what forbids you from doing what your companions ask you to do? Why do you read this Surah particularly in every Rak'a?" He repiled, "I love this Surah." The Prophet ﷺ said, "Your love for this Surah will make you enter Paradise." 
Abu Darda reported Allah's Apostle ﷺ as saying: Is any one of you incapable of reciting a third of the Qur'an in a night? They (the Companions) asked: How could one recite a third of the Qur'an (in a night)? Upon this he (the Holy Prophet ﷺ) said:" 'Say: He is Allah, One' (Qur'an 112) is equivalent to a third of the Qur'an." 
The believer benefits in knowing that Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ is Al-Ahad. We realize what it means to be truly unique. Allah is the one and only Creator (Al-Khaliq), the one and only Provider (Ar-Razzaq). As the title of the Surah Ikhlas (meaning 'sincerity') suggests, we turn to Him with the purest intentions to seek His mercy, love, and acceptance. We also learn of the extensive rewards that's gift-wrapped for the believer in reciting Surah Ikhlas.
We can reflect on this name by asking ourselves how we are unique. What admirable qualities do I possess or wish to develop? What are attributes honorable in the sight of Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ often neglected? It's easy to conform and blend in with the masses. In fact, we may unconsciously do this so as to not be ostracized from standing out. Instead, we should recognize how Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ made us unique and be grateful to Him. Don't fall for the dreams people sell that you should be like them, which can only be achieved by purchasing their product. This is a chase that will lead to unfulfillment. True contentedness is through acceptance and gratitude for what Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ has given you.
Supplication from hadith:
Allahumma inni as'aluka ya Allah bi'annaka 'l-Wahidu 'l-Ahadus-samad, alladhi lam yalid wa lam yulad, wa lam yakun lahu kufuwan ahad, an taghfir li dhunubi, innaka anta 'l-Ghafurur-Rahim.
"O Allah, I ask You. O Allah, You are the One, the Only, Self-Sufficient Master, Who was not begotten and begets not, and none is equal to Him. Forgive me my sins, surely you are Forgiving, Merciful." 
 Mishkat al-Masabih 2185
 Sahih al-Bukhari 774b
 Sahih Muslim 811a & Riyad as-Salihin 1010
 Sunan an-Nasa'i 1301