Answer by taking a quote from the following article:

Bertrand Arthur William Russell, 3rd Earl Russell,  (; 18 May 1872 - 2 February 1970) was a British philosopher, logician, mathematician, historian, writer, social critic, political activist and Nobel laureate. At various points in his life, Russell considered himself a liberal, a socialist and a pacifist, but he also admitted that he had "never been any of these things, in any profound sense". Russell was born in Monmouthshire into one of the most prominent aristocratic families in the United Kingdom. In the early 20th century, Russell led the British "revolt against idealism".

Russell won a scholarship to read for the Mathematical Tripos at Trinity College, Cambridge, and commenced his studies there in 1890, taking as coach Robert Rumsey Webb. He became acquainted with the younger George Edward Moore and came under the influence of Alfred North Whitehead, who recommended him to the Cambridge Apostles. He quickly distinguished himself in mathematics and philosophy, graduating as seventh Wrangler in the former in 1893 and becoming a Fellow in the latter in 1895.  Russell first met the American Quaker Alys Pearsall Smith when he was 17 years old. He became a friend of the Pearsall Smith family - they knew him primarily as "Lord John's grandson" and enjoyed showing him off. He traveled with them to the continent; it was in their company that Russell visited the Paris Exhibition of 1889 and was able to climb the Eiffel Tower soon after it was completed.  He soon fell in love with the puritanical, high-minded Alys, who was a graduate of Bryn Mawr College near Philadelphia, and, contrary to his grandmother's wishes, married her on 13 December 1894. Their marriage began to fall apart in 1901 when it occurred to Russell, while he was cycling, that he no longer loved her. She asked him if he loved her and he replied that he did not. Russell also disliked Alys's mother, finding her controlling and cruel. It was to be a hollow shell of a marriage and they finally divorced in 1921, after a lengthy period of separation. During this period, Russell had passionate (and often simultaneous) affairs with a number of women, including Lady Ottoline Morrell and the actress Lady Constance Malleson. Some have suggested that at this point he had an affair with Vivienne Haigh-Wood, the English governess and writer, and first wife of T. S. Eliot.

What did he study there
He quickly distinguished himself in mathematics and philosophy, graduating as seventh Wrangler in the former in 1893 and becoming a Fellow in the latter in 1895.