The 3 main envelopes are quite flexible, with multi-stage attack and release, and shape control over each stage. The controls are laid out as in this diagram:
Other envelopes (the amplitude envelope, the pulsewidth envelope and the filter envelope) have subsets of these controls.
Each envelope has 3 attack stages, a sustain stage and two release stages, and you can specify a time for each, as shown here:
The shape controls correspond to the five time controls. They change the segment shape between linear and curved.
There are four level controls, which set the envelope level at the points between the stages: