Lessons at a chalkboard, level by level
A course that runs A1 to C1, written one step at a time as you take it. Your teacher works at a board, builds her examples out of your own mistakes, and never announces what's coming.

Conversations teach you a great deal and no particular order. A course is the other half: somebody deciding what comes before what.
What changed
Lessons is a course with levels now — A1 through C1 — each holding a set of lessons chosen for the language you're learning. You work down them.
A lesson happens at a chalkboard. Your teacher writes one idea on it at a time and talks you through it, and the examples she uses are built from mistakes she's actually watched you make rather than from a textbook. Then she asks you something about it.
Written as you take it
Each step is written when you reach it, not in advance. That has a real consequence: a lesson can follow what you did two steps ago. Get the instrumental case wrong in the first exercise and the third one is about that.
It also means a lesson never tells you what it's about to teach you. You find out by doing it — which is how a good teacher works, and a syllabus doesn't.
It keeps your place
Leave in the middle of a lesson, close the tab, come back on a phone two days later: it opens where you left it, on the same step.