Short answers, pulled from the story.
The Second Anglo-Maratha War began on the 2nd of December 1802 with the signing of the Treaty of Bassein. This treaty was signed by Baji Rao II, the Peshwa of the Maratha Confederacy, after his armies were defeated by Yashwantrao Holkar at the Battle of Poona.
Major General Arthur Wellesley, later known as the Duke of Wellington, led a force of 24,000 men to attack Maratha forts. Lieutenant General Gerard Lake was tasked with taking Doab and Delhi, while other commanders like Powell and Murray led separate columns in the multi-pronged assault.
The Maratha Empire lost significant territories including Cuttack, Hisar, Panipat, Rohtak, Rewari, and the Delhi-Agra region. The Treaty of Surji-Anjangaon signed on the 30th of December 1803 ceded these areas to the British East India Company along with parts of Bundelkhand and Gujarat.
The war concluded with the Treaty of Deogaon signed on the 17th of December 1803 and the Treaty of Surji-Anjangaon signed on the 30th of December 1803. The conflict officially ended with the Treaty of Rajghat signed on the 24th of December 1805, which forced Yashwantrao Holkar to cede Tonk, Rampura, and Bundi.
The Maratha Confederacy lost due to internal quarrels among the five major chiefs including the Gaekwad, Scindia, Holkar, and Bhonsle rulers. The British exploited these divisions by using subsidiary treaties to turn the chieftains against one another and systematically dismantled their military power.