This walkthrough from Mastering.com covers the LFO and modulation envelope in Logic's ES1 synth, showing how to route them to pitch, cutoff, or volume for vibrato and swelling effects.
The LFO rate can run free in hertz or sync to tempo, with depth controlled by how far you turn up its amount, or opened via the mod wheel.
The modulation envelope uses its own attack, decay, sustain, and release to shape how a parameter like pitch evolves over the note, separate from the amp envelope.
Beyond modulation, the bit touches on voice count for switching between mono and poly, the built-in chorus and ensemble effects, and the analog character control that randomizes pitch and cutoff slightly for a less sterile, more analog feel.