bottom line, bull's-eye, centerpiece, core, crux, essence, gist, heart, kernel, keynote, meat, meat and potatoes, net, nub, nubbin, nucleus, pith, pivot, point, root, sum

course, direction, drift, tenorbody, content, substancehypothesis, proposition, purport, subject, theme, thesis

the long and short(or the long and the short)