The stated goal of the Crusades was to recapture the Holy Land from Muslim forces, but there were also many unstated goals which European lords and clergy strove to achieve.
Originally, the pope had called for a crusade to capture important Christian holy sites, such as Jerusalem, from the forces of Muslim rulers. These military operations were launched in response to calls for support from the Byzantine Empire who had been under attack by Muslim forces for many years.
The rulers of the Holy Roman Empire had their own agenda as well. Centuries of fighting between feudal lords had produced a surplus of warriors that rampaged across Western Europe. The Crusades provided rulers with a novel way of emptying their realms of their more violent element while increasing their own virtue, prestige and riches. The more pious rulers saw it as an opportunity to win forgiveness or absolution while the less pious saw the potential wealth that could be gleaned from controlling part of the holy land.
Later, the aims of crusades changed. Some targeted heretics such as the Cathars. Others targeted pagans or excommunicated Catholics.
There were several different Crusades and the motivations of both the leaders and the participants varied. In the eleventh century, Islamic empires expanded, conquering areas previously under the influence of the Byzantine Empire. Thus there were two main stated goals to the Crusades.
The first goal was to reclaim the Holy Land (Jerusalem, in particular) from Islamic control, making it safe for Christian pilgrims. The second goal was to come to the aid of the Byzantine Emperor, a fellow Christian ruler.
In this period, it is important to note that post-baptismal sin was considered extremely heinous. The Pope offered plenary indulgences to Crusaders. This meant that many Crusaders were motivated by this offer, especially if they had committed mortal sins.
A far less savory reason for going on the Crusades was the belief in the great wealth of the East and the opportunity for lucrative plunder.
Goal of crusades were to kill the Muslims, recapture the Holy Land and produce a secular state.