EtherChannel: multiple links, a single port
Every mechanism gets a step-by-step animation, the configuration explained line by line and the exam notes. Where a parameter changes the outcome, there is a simulator where you change it yourself.
TL;DR
EtherChannel groups up to 8 physical links into a single logical interface. STP sees it as one port, so it blocks nothing, and routing sees a single adjacency. The ports must be configured identically; LACP (or PAgP, on Cisco) verifies before bundling that the other end really is the same channel. Traffic is split per flow, through a hash — one flow never exceeds the speed of one member, and the choice of hash fields decides how well the links are used. A member failure is absorbed in milliseconds; min-links, standby ports, channels towards two switches (stack, VSS, vPC), micro-BFD and EVPN all-active complete the picture.
How to read the notes: red = critical for the exam, green = theory, blue = numbers, yellow = pitfalls, cyan = IEEE ↔ Cisco differences. In the animations, the configuration lines used at the current step are highlighted automatically; the ← → arrows change the step when the animation is focused.
The analogy, in short
Think of a four-lane motorway instead of four separate roads. The lanes share the same rules, the two cities confirm to each other that they are talking about the same motorway (LACP), and every car gets a lane at the toll gate and never changes it (hash).
The model holds up to §7. From §8 onward (vPC, micro-BFD, EVPN), it breaks; see the full analogy and its limits in §12.