The Baltimore Catechism was compiled by the order of the Council of Baltimore. There were a series of local Councils of the bishops in the U.S. which delt with the moral, spiritual and practical matters of practicing the Catholic Faith in the U.S. after independence from England. There were any number of issues that had to be solved, some of them were referred to Rome, others decided on the local level. The education of Catholics was one, and the Catechism was one of the answers. The modern day alternative to the Councils of Baltimore would probably be the USCCB.
All catechisms as illuded to above, be they the Baltimore, or the Penny (in England), Fr. Hardon’s or any other, including the Catechism of the Council of Trent (intended as a guide for priests to assure that they covered the faith more fully with their congregations) are a distillation of the teachings of the Church. Much the same as a driver’s handbook that State Motor Vehicle departments issue for the driving exams. They don’t encompass all the traffic laws of the State that issues them, but are a simplified guide for someone who is taking a license exam.
Catechisms are a good starting point in learning the Faith, and hopefully will spark a desire to learn the Faith more fully. There are charges against the Church by some anti-catholics against Catholics that they use the Bible alone, and that Catholics use their Catechims. If they really read through a copy of any good Catholic Catechism, they would find in the information that is covered, and in the footnotes that the catechism does not replace the Bible, but is a great source of learning the meaning of the texts of the Bible, and the rich theology derived from it.