Kraftwerk is an industrial electronic music group and was very experimental. They're musical style was ever changing originally with there first few albums Kraftwerk had common instruments like flute and guitars and were more open and free form rock but as they moved on with 'Ralf and Florian' they moved more toward an electric sound. That album also featured what would be a signature mainstay in later releases, the use of vocoder.
They were not like musicians who were popular at the time with beards and long hair they were very organized and were in line. They would play in suits and would have kept hair with clean shaved faces like in the cover of 'Trans-Europe Express'. Ralf and Florian were the leaders and primary songwriters of the group. With just about every album they made there was a concept behind it whether it was nuclear energy and radio in 'Radio-Activity' to road travel with the 'Autobahn'. Autobahn, released in 1974, was a successful album for them and the title track even though it was originally a very long track, 22 minutes, after edited and released as a single was a pop hit.
Not every album was as successful and albums like Trans-Europe Express were a commercial flop but it was unique. They wanted the music to sound like a train that was moving. They're music inspired many people including a famous superstar who actually moved to Germany partly because of them. David Bowie who's last album had some synthesis but also folk music with the next to albums with Brian Eno they introduced electronic music to the masses with the albums, Low and Heroes.
Kraftwerk was influential to many and as a fan of music I appreciate that and as a student learning about music history anyone who brings something fresh and new I like but even though I'm not a particular fan of their music I respect that.