Luther started a part of the reformation, at basically the same time in Switzerland Zwingli started one as well. Luther's became Lutheranism and Zwingli's the Reformed movement.
Lutherans basically were Catholics with slight differences on a few issues (consubstantiation as opposed to transubstantiation, matters of justification). They wanted originally to change the RCC, move it back towards the truth (as they saw it).
The Reformed movement under Zwingli was much more radical. They rejected much more of what Roman Catholicism taught and didn't so much change what was wrong with the RCC (in their eyes) as they did try and start all over with a more Biblical model.
Now there was a time where Luther and Zwingli met to try and form some sort of 'union' or 'unity' between themselves, but while Zwingli was willing to forge it, Luther was not. Luther was adamant that Christ was in the Lord's Supper (consubstantiation) while the Reformed movement saw it as symbollic. Luther was not willing to have any fellowship as long as that issue separated them.