Booker T. Washington was a emancipated slave who became a self made man. He advocated for a 'realistic accommodation' and 'self help'. He founded the Tuskegee Institute in hope to promote a vocational education for the disenfranchised African Americans some 15 years after the end of the Civil War. Washington argued that the only way African Americans could secure their political equality was to 'dignify and glorify common labor'. Booker T. Washington believed that only after African Americans proved themselves as achieving citizens, their political freedoms (rights) would come to them. Booker T. Washington had his critics, among the most vocal included W.E.B. DuBois.
Washington was also primarily concerned with education for black Americans, and this was one of the reasons why he was so accomodationist - he was seeking concessions from the white southern governments for black schools. His Atlanta Compromise, as it came to be known, basically accepted blacks segregated status in return for more education funding (though, as DuBois pointed out, no one had elected him King of African-Americans to accept such a deal). Washington founded the Tuskegee Institute and a string of what are now known as "traditionally black colleges" such as Spelman University, in hopes that blacks could raise themselves to equality through their own education.
Historians have a love him or hate him type of view towards Washington for his compromises on civil rights, but for the time he lived in, it's hard for me to see what more was possible.
Booker T. Washington opposed WEB DuBois in an important dispute over how blacks should push for rights in the late 1800s. Washington was, in general, much more accomodationist and patient that DuBois.
Washington is famous for a speech at the "Atlanta Exhibition" in which he urged blacks to be humble and patient. He said that they should work hard and be humble. If they would do this, whites would come to see that they deserved to be treated with respect. That is how they should fight for their rights.
This is why Washington is seen as accomodationist -- he wanted to act in ways that would accomodate white views. He did not want to really push aggressively and demand rights.