How to find unique elements in a cell array

I am trying to search through a cell array that holds both strings and integers. This cell array is sorted via the third column. In the second column is a list of majors for the students that where given by the user. I need to search through this second column and pull out only the unique majors and put them into a list to be used with listdlg, that then upon selecting the major from the list shows the user which people in the cell array share the selected major. The code of what I have can be found below.

information = {};

for i = 1:5

prompt_1 = {'Name','Major','Grad Year','Lucky Number(s)(use [])'};

dlg_title = 'User information list and compare';

num_lines = 1;

def_1 = {'John Doe','AE','2015','[1 33 7]'};

answer = inputdlg(prompt_1,dlg_title,num_lines,def_1);

information{i,1} = answer{1,1}; %#ok<*SAGROW>

information{i,2} = answer{2,1};

information{i,3} = answer{3,1};

information{i,4} = answer{4,1};
end

%sorted by graduation year information array

sortedinfo = sortrows(information,3);

Answer 1

[Andrei Bobrov]

[a b c] = unique(sortedinfo(:,2));
[id,id] = sort(c);
out = mat2cell(sortedinfo(id,:),histc(c,1:max(c)),size(sortedinfo,2));

[Matthew]

Would you mind explaining what exactly is going on with the 2nd and 3rd lines of code?