Simply stating for a layman:

Muhammad Bin Tughlaq was the Aurangzeb of Delhi Sultanate.

Mughals were at the peak of their power under the reign of Aurangzeb, similarly the sultanate was at the peak of its power under Muhammad Bin Tughlaq. However, both of them were responsible for the decline of their respective empires due to their wrong policies and over stretching of resources.

Both of them saw the resurgence of the Hindu kingdoms. While Aurangzeb had to face the Marathas, Sikhs, Jats etc., Muhammad Bin Tughlaq had to face the Rajputs in the North and the newly established Vijaynagara empire in the South.

(Read a comprehensive summary of the Delhi Sultanate: Ankit Pandey's answer to Which was the most successful of the five dynasties that ruled the Delhi Sultanate?)

A Man whose ideas fell like a deck of cards :

Alauddin Khilji had already demolished many ancient Indian kingdoms and had successfully encroached South India. To get a more centralized capital to govern the Southern part of his empire, Muhammad Bin Tughlaq tried shifting his capital to Daulatabad. However in doing so, he ruined the city of Delhi which in terms of the volume of trade once rivaled the cities of Baghdad and Cairo. Similarly, the failure of his demonetization experiment further strained the resources of the Sultanate.

During the reign of Tughlaqs, Mongols in the northwest had weakened. Muhammad saw this as a chance to invade the Mongol lands and raised a huge army. However even this experiment failed, creating serious financial problems for the Sultanate.

However these failures did not stop this ambitious ruler who sent an another expedition against the Katoch Rajputs of Himachal. Highly experienced in the mountain warfare, Katoch Rajputs dealt an embarassing defeat to the Sultan. Of the entire invading army of 100,000, only the commander and a few other men managed to return to Delhi.

The twin Hindu resurgence in North and South India:

North: With the fall of Chittor and Ranthambore, almost all the Rajput resistance had ended. However, a distant relative of the martyred king of Chittor, Rana Hammir recaptured Chittor with the help of his quick witted queen. The Rajput resistance had once again started in the North India. To quell this uprising, Tughlaqs fought the Battle of Singoli in which Rana Hammir dealt an embarrassing defeat on the Tughlaqs and the entire Rajputana was freed from the sultanate. Rajputana would now stay clear of the Muslim rule throughout the rule of the next two dynasties that came to power in Delhi – the Sayyid and the Lodi dynasty. The Lodis repeatedly tried to reassert their control, however, they lost, once again, to the Ranas of Mewar.

South: Before the rise of the Vijayanagara Empire, the Hindu states of the Deccan — the Yadavas, the Kakatiyas, the Pandyan empire of Madurai had been repeatedly raided and attacked by the Sultanate, and by 1336 these upper Deccan region had all been defeated by the armies of Muhammad Bin Tughlaq. Further south in the Deccan region, a Hoysala commander declared independence and established the short lived kingdom of Kampili. It ended after a defeat by the armies of Delhi Sultanate who carried the straw-stuffed severed head of the dead Hindu king. The womenfolk committed jauhar. Eight years later, from the ruins of the Kampili kingdom emerged the Vijayanagara Kingdom under the brothers Harihara and Bukka who began liberating the lands of South India.

The over ambitious Sultan was forced to witness the compression of his empire under this twin fold resistance, which a few decades earlier was responsible for the demise of so many native kingdoms. He finally died on his way to quell a rebellion of Gujjars in Sindh.

So, basically Muhammad Bin Tughlaq’s reign was the point from where the decline of the Sultanate started.