I am reading an overview of the beacon chain here and I came across this section I do not understand:
Validators are split into “beacon committees” at each epoch (defined 1 epoch in advance to allow for preparation). Each committee is assigned to a slot (and shard in Phase 1). And each validator in the committee attests to the head of the beacon chain (and the recent data of their assigned shard) at their assigned slot
What does "attest to the head of the beacon chain" mean? Does the head of the beacon chain mean the latest block on the beacon chain? If so what does it mean to attest to it?