Minimal techno is an offshoot of Detroit techno. It's heavily influenced by such minimalist composers as Steve Reich, i.e. it features repeating short patterns (ostinati) that slowly change in character. The two godfathers of minimal techno are Rob Hood (with Minimal Nation) and Dan Bell (with "Losing Control" as DBX)
Most minimal techno tracks are best experienced as part of a DJ's set, or from a live act.
A lot of minimal techno comes from Sweden from guys like Adam Beyer and Christian Smith. This particular style became very well known and is quite possibly what someone will think when the word "techno" is heard, assuming that person is into jungle or breaks or house or whatnot.
Minimal techno has influenced the creation of what is called minimal house or microhouse.